These sites are good for finding information on airsoft:

Wolverine Tactical Supply (closed down, not sure if their site is still up. They sold out to 21st century airsoft)

Wargamer's Shop (check here for new stuff in airsoft world, or if you want to order from overseas)

Cimmerians (the original and the standard in USA airsoft)

Redwolf Airsoft (another cool overseas site)

Shorty USA (sometimes they have cheap stuff, but its usually just that)

MIA forums (more help then you could imagine)