Hey! I've found a project (most of you maybe already know, but for me it's new) called DoomsDay. They've now made doom compleletely 3d using openGL. Including 3D models for monsters and items + extra things like barrels, pillars etc. Lights are enhanced, and you can play multiplayer over the internet. Although there aren't any public servers yet (anymore...).
The site of DoomsDay is here:
http://www.doomsdayhq.com/
BTW, you'll need your own wad file though (doom.wad or doom2.wad). Playing shareware is also possible using doom1.wad! You can also play heretic or hexen with this program!