There are a lot of Aussie clans out there doing the "full tac" (100% tactical-zero-casualties) stuff that really brings out the full game. This clans can be hard core military (my style) or it can be more casual Tac (NotoriousD) style. Either way, if you're playing with a good squad leader there is nothing more thrilling than having you and your mates prone in the treeline listening to the correct military jargon for calling in an artillery strike over Teamspeak, seeing it "splash down" bang on target and when the dust clears 20 seconds later there is the satisfying "enemy neutralised - fire mission complete" damage assessment report.
Maybe your thing is to lay down constant suppression fire alternating with your MG buddy while a rifle section flanks the bad guys who can't be bothered to lift their head in case it gets shot off.
Maybe you like being the medic who needs to wait for the call to rush into an open field under the safety of debilitating cover fire with only smoke between you and the enemy to conceal your movements
If you have a joystic then mplayer clans are always looking for talented chopper pilots who can do a hot extraction in a tight clearing to save some SAS RECON squad who strayed a little too far behind enemy lines.
Or - if you don't want to do any of the above - I'll link you some good single player missions.