Rainbow Six
Call of Duty 4
Ghost Recon
Splinter Cell
Halo

Clans

Smokin Gunz
Indefinitive Corruption
Assassins Guild
XGL
The Last Shot
Cold As Ice
Clan MoD

Resources

Xbox Live - The guide Knackered NAT, look here for help
Major Nelson The inside view of Xbox Live
Official Combat Competitive ladder site
Your Friends list See which clan members are online