BFTA www.thebfta.net The national FT organization. The two training manuals are very useful, even if you don't want to shoot FT.
SWEFTA www.swefta.org.net The local region, what's on in the South West.
AIRGUNBBS www.airgunbbs.com Very popular airgun forum for info, chat and banter.
STB www.shooting-the-breeze.com Another popular forum, very informative.