cryptrader.com was fairly crowded for some time. Also quite a community at twitter.
Other than that there's countless reddits and teamspeak chatrooms, IRCs and what not. Most are invite only. But be careful with the IRC's because your computer could be infected with malware. Don't use the trading machine for IRC.
For tracking prices most people use
http://coinmarketcap.comI absolutely love coinmarketcap, I've been roving it a lot. I think they have the best up to date prices and easiest to understand information of any site I've found so far.