This is just a sketchy list of things DOS is capable of. I concentrate on the things less obvious, and most of the time I only give one program as an example, which is not to say that there aren't more.
Mpxplay is a free DOS mp3 player that can handle wav files, too. Damp is another one, it can read WinAmp playlists and create funky visualisations. A 486 DX4/100 is usually given as the absolute minimum, but I guess you should have a Pentium for that.
QuickView can play avi, mpeg, mov and several other video formats, view most image files and play wav, voc, and mp3 files.
There are special mpeg cards that will allow you to play mpeg videos on a 386. They usually have their own player software.
DosCDroast is still in beta, but it is completely free and runs under 16-bit DOS. It supports CDR, CDRW, DVD/R and DVD/RW; IDE/ATAPI, SCSI, Parallel Port, USB, and other external devices.
Ironically, I am not aware of any driver capable of reading CD-RWs; there are problems with CD-Rs too, if they exceed a certain size.
Adobe Acrobat Reader is available for DOS as well. A good video card is required for this one (at least 2MB, I guess) and you should run it at the highest possible resolution.
NeoPaint isn't PhotoShop, but it's a powerful graphic program (screenshots), fits on a floppy and can run on a 286 if necessary. A screen capture utility is included.
Arachne is a graphical web browser, unfortunately, though of considerable charm, not necessarily one of the best. It has no support for JavaScript, limited support for stylesheet and sometimes rather unorthodox interpretations of HTML commands. On the other side, it can be used as a general graphic user interface for DOS. It has an integrated text editor, QuicKpad, and with the help of packages (that are more or less like Netscape plugins) you can view pictures in various formats, watch movies or listen to mp3 music.
And of course there is a DOS version of Lynx.
