http://www.quaddicted.com/quake/re... -> quakespasm. cross-platform and makes a fine server too.
http://www.quaddicted.com/quake/co... has some notes on multiplayer, you will need other things for deathmatch of course.
Play
http://www.quaddicted.com/files/ma...
http://www.quaddicted.com/files/ma...
http://www.quaddicted.com/files/ma...
If you are more than 4 people, try the efdm* maps and dranzdm7. I lost my notes on maps I think.
I once made a pack of nice maps
http://www.quakeworld.nu/forum/top...
Sorry for the quaddicted spam.