For quake2 check out these links:
http://www.icculus.org/quake2/
http://www.chez.com/colinf/quake2/CD-MP/quake2-r0.15-io1.i386.rpm
for quake3:
ftp://ftp.idsoftware.com/idstuff/quake3/linux/linuxq3apoint-1.32b-3.x86.mun
These files will install the games. You will need to copy the game data off of your cd's or from your windows installations. You have to have 3d working under linux with a voodoo, nvidia or ati card first.
After you get quake3 working you should check this out:
http://www.urbanterror.net/
