I am the owner and administrator of the #S-Run Shadowrun Community , the world's most active IRC-based Shadowrun role playing community. We have games running almost nightly and are always looking for new patrons to come and enjoy a game (or even just chat) of Shadowrun on IRC.
The website has a handy FAQ for the IRC un-savvy, and a Java-based Chat to make things easy as well. There are also forums, and a shop up.
Personally, I have every english-language Shadowrun novel written, as well as almost all the sourcebooks except a few choice ones I'm lacking. Some of them I wouldn't buy regardless (pretty much anything SURGE or YotC-related) because I don't like the idea of trying to canonize furries in a dystopic cyber-future.
In SR4, the game has definately lost its 80's cyberpunk flair, but this new 'cybertech' style is nice, too. I'm even starting to play it after hating on the changes for a good 2 years. My campaign (Chronicles of the A-Team) will remain SR3 until it ends...But the sequel will be SR4.