(Note: This site was originally made only for the PvP Forum, so it contains a few inside references. Sorry 'bout that.)
For a good webcomic listing, visit The Belfry. The Belfry was originally a furry listing, but it has since expanded into 'normal' webcomics as well, and now maintains one of the best listings found online. Strips are grouped by update frequency and content warnings (Jack, for example, gets the full list...). Anything that gets a 'Foxen's Fav' rating at Belfry is definitely worth checking out, and most of the non-starred ones are great as well. Just stay away from stuff with too many red letters next to it unless you know what you're looking for :D.
Funny:
Penny Arcade is pretty much a must-read if you want to understand people on this forum. Most quotable webcomic ever.
Ctrl+Alt+Del is another gaming strip, one of (probably) millions out there. So what makes it list-worthy? Well, it made me laugh. That's far more than 99% of the gaming strips I've seen managed. Art is nice, characters are funny...all above-average quality. Solid strip.
Something Positive is always insensitive, sometimes gross, often offensive and funny as hell. Davan may just be the greatest concentration of cynicism ever to walk the earth, a kind of cynical singularity, a black hole of dark thoughts. Read this and feel bad about laughing.
8-Bit Theater is the quintessential sprite comic. Sword-chucks, hadokens, mass stabbings and min-maxing combine to form perhaps the funniest look at Final Fantasy ever.
Mac Hall doesn't update anywhere near as often as it should, but unlike with certain other strips, it actually pays to wait. There hasn't been a single Mac Hall strip so far that hasn't at least made me giggle.
VG Cats is well drawn, has a unique style and does the 'make fun of video games' thing better than a good 90 percent of the 'gamer comics' out there. Definitely worth a read.
Bruno the Bandit is one of the best fantasy parody strips out there, although the puns will frequently leave you groaning. They're worse than what Doc Otto over at PCC used to pull :D.
Lizard is an odd mix. One-third 'feel-good' strip, one-third soapish material, with the rest being random humor that makes 'shroom-induced hallucinations seem coherent by comparison. It's very, very hit-or-miss (being a Dave Kelly comic), but it's at least worth checking out. You may be one of the few who enjoy this particular brand of humor.
Newshounds has extensive archives going back to 1997 and is full of reportery goodness. Liberal readers may feel a slight urge to kill Sam, while the opposite side will have similar feelings about Alistair, so things sort of balance out in the end :D.
Real Life has been mentioned before, but I'll just have to mention it again: It's that good. Even though Greg can't draw hands :D.
S.S.D.D. is another one of those hit-or-miss things. If you can stomach brit furries and the...well, somewhat shitty art in the beginning, you might be able to enjoy the misadventures of a very odd group of friends (and some visitors from the future).
Schlock Mercenary is another strip that's visibly come a long way, art-wise. The writing, though, has been top-quality funny from the very beginning...and it's also one of the very, very few sci-fi-themed strips that pays attention to such things as 'physics' or just science in general.
InkTank has two very funny strips running (Angst Technology and Weekend Warriors), both are definitely worth checking out.
Sluggy Freelance is a true classic of the webcomic scene. It's been around since the dawn of the internet, practically (well, since 1997. That IS pretty damn old, for a webcomic). It's also insanely funny and funnily insane.
Kevin and Kell is unusual in that it's the 'side project' of a man who makes his living drawing syndicated newspaper strips. It's also unusual in the fact that it's about a family of animals that somehow manage to ironically reflect every facet of human existence. It's also full of computer jokes, if you like that sort of thing, while not being as...well, as UF as User Friendly.
Ozy and Millie is also quite unique. It's been described as 'Calvin&Hobbes with foxes'. That does neither C&H nor O&M justice, really. It's a very, very funny strip about children. And dragons. And pirates who live under the sofa.
Angels 2200 combines several features of successful comics and TV series, as an all-female crew of misfits has to come to terms with each other and their role as fighter pilots in an interstellar war (which is, incidentally, waged between all-female armies). Zaniness, space action, lesbian undertones (or heavy overtones, in the case of one character) and a nice art style make this at least worth checking out once.
Freefall is yet another sci-fi parody strip, featuring the world's dumbest robot, an alien captain whose ship is trying to kill him and an engineered (genetically) engineer. Definitely one of the better examples of that genre.
Sabrina Online is yet another classic, going back to 1996. It only updates rarely, but it never fails to be funny. The lead character, incidentally, is a female furry (skunk) webdesigner who collects transformers, prefers to use Amigas and works at a porn studio. Beyond that, she is remarkably sane. Any more questions?
Checkerboard Nightmare is drawn by Airsick Moth. Let me repeat: Air. Sick. Moth.
If that doesn't convince you of the strip's quality, you're beyond help :D.
Faux Pas is a simple, lighthearted and thoroughly funny strip about a bunch of 'animal actors'. You know, the kind of critter you see in pet food commercials, or as 'animal nr. 3' in TV series. Characters include a soap-opera-loving chicken, an ever-growing family of rabbits, a frequently-confused kangaroo and a fox who needs to come to terms with the fact that he's absolutely and completely domesticated.
The Whiteboard is a 'minority comic', so to speak, as its particular sense of humor is tailored towards a very specific group of readers: Paintball players. That doesn't make it unfunny for non-paintballers. Not by a long shot. So do yourself a favor, click this link and discover the secret life of paintball-playing polar bears...
Roomies is another decent furry strip. Funny, cute, and occasionally even fairly deep. If you don't mind talking animals, take a look.
Alter Meta's slogan is 'Sex, Dragons and Rock & Roll'. Well, the 'Sex' part is exaggerated, the rest, fortunately, isn't. It's teen comedy, simply put. You've got all the necessary sitcom stereotypes...the badass muscle chick, the tomboy, the geek, the self-styled starving poet, the cheerleader...and so on. And Alter Meta mixes it up, shakes it a little, adds a cool world populated by dragon-people, stirs and serves one of the best overall funny comic experiences I've had in recent months.
Drama:
(note that drama strips might very well include humor - in fact, most do. Just don't expect a laugh every four panels.)
Clan of the Cats has witches, werebeasts, vampires, wizards and ghosts. It's also at once funnier and more serious than that POS TV series 'Charmed', which would be the closest equivalent, setting-wise.
Suburban Jungle. Why the hell did I put that into the drama section? Well...it's usually funny, but it's also one of the most soap-opera-ish strips I know. That, however, doesn't necessarily make it bad. It's usually worth at least a smile, and that's more than you can say about most webcomics.
Wandering Ones is an adventure strip in the proud tradition of such classics as 'Prince Valiant'. Yeah, you didn't misread. There are certain...similarities in the art style, too. It's not high literature by any stretch of the imagination, but it's entertaining. Sort of like your average action movie...only in the post-apocalyptic future.
Jack. You knew I was going to mention it, didn't you? It's a dark, often disturbing and DEFINITELY NSFW strip about hell, damnation, the nature of sin and the afterlife. To give you an indication of the nature of the strip...the main characters are the personification of the Sin of Wrath (a mass murderer of sorts), a kid who died before he was born and an angel who lost her wings and now has eternally bleeding stumps in their place. And those are the more positive characters. Go through the archives. You'll hate it or you'll love it, but for this first trip through hell, there won't be a grey area.
Shifters is sort of the light side of the World of Darkness. Werebeasts, Vampires and other supernaturals do exist in this futuristic world, hidden behind a mutual agreement called 'The Veil'. The Veil is held together by a careful balance of power, and threatened by the near-eternal cold war between vampires and weres.
And the accidental introduction of a teenage girl into the Veil is about to escalate this conflict into an all-out war...
Just read it. Have patience with it, the art starts out REALLY bad. Believe me, it gets better. A lot better.
Outsider is updated even more sporadically than Megatokyo. But when it does update, this incredibly well-drawn sci-fi story is always worth the wait. There's only a handful of pages so far, but they are truly awesome, every one of them.
Lacunae is dark, gothy, angsty and furry. If that doesn't scare you away, it's a well-drawn, well-written strip that takes a somewhat unusual approach to the myths of vampires and similar 'monsters'. If you read Jack, the main character should be familiar to you: It's Silverblue, the gothbunny :D.
Utukki is drawn by a forum regular. That said, it'd be on my weekly to-read list without that link as well, as it's just damn good. Good art, good writing, an interesting storyline...very nice.
Sacred Pie may have a pretty weird name (and some odd concepts as well), but it's actually a rather cool semi-serious sci-fi/fantasy story with pretty good art (starts out rather similar to early PA, actually). If you want to read about three 21st-century teenagers taking on the forces of Satan in the far future, this comic may be for you.
And finally...
Cyantia at least deserves mention, if not for quality (which isn't too bad, though) then at least for quantity: Tiffany Ross is probably one of the most active webcomic artists in the world, constantly working on at least 4 active projects at the same time, with countless others being on-hold or in planning. Many of those are set in the world of Cyantia, which is essentially our modern earth with extra aliens. Two of her strips I particularly like are Alien Dice (Imagine if pokemon was real. What would those little things feel, forced to fight pointless battles over and over again?) and Pure (which combines 'supers' and dystopian elements along the lines of 1984 and Brave New World).