You'll also need GLSetup to run Quake 3.

Patches
Expansion Pack - Gernade Launcher and BFG introduced, plus 2 new maps! New skins!
HH Pack (Return to Blood) - Awesome add-on! Makes the items, and sounds much better! Download!

Maps
Tim map - Map is too small. It gets old.
Rail Map - Q3test1 and Q3test2 maps with just rail guns for weapons

Skins
Swat-Visor
Senkusha
Quadmaster
Visogro
Chaos
Unknown
Sarge
Lore
Diamatrix
Militant
E-8
Celtic
Spread-Eegle
Metalice
Reznor
Seven
U-drokker
Kurgan
Cold-Steel
Clank
Azreal
Ramshield
HellsHound
Death
Hunte
Impulse
Xaero

Videos
q3aqamov1 / 3900 kb - QuickTime movie showing off id Software's upcoming Quake III Arena
q3aqarena1 / 23055 kb - This demonstration of Quake 3: Arena given at Macworld shows a tour of a test level and showcases many of Quake III Arena's new features
q3aqdemome1 / 1600 kb - This is an inofficial movie of q3test play om a g3 mac
q3aqea1 / 9420 kb - Videos of the Quake III Arena demo displayed at the CPL Extreme Annihilation event
q3aqea2 / 9940 kb - Videos of the Quake III Arena demo displayed at the CPL Extreme Annihilation event
q3aquakehi1 / 674 kb - This a demo showing off the new Q3Arena test for the Macintosh. The demo is centered around multiplayer deathmatch
q3ashaunad1 / 1900 kb - Shauna player model animation. This model will not be in the final game but it will be in a model pack due to be released sometime after Q3A is out

Misc
Q3A Name Builder - Put colors or different fonts in your name while playing Quake 3.