Forums

General Bitcoin Discussion

• BitcoinTalk Forum (formerly located at Bitcoin.org)
• Bitcoin Subreddit
• BitcoinForums.net
• Bitcoin TweetForum
• Bitcoin-Board Forum
• Bitcoin google group
• Bitcoin Trading Forum

Language/Region Specific

• Australian Bitcoin forum
• Italian Bitcoin community forum
• Polish Bitcoin community forum
• Russian Bitcoin community forum
• United Kingdom Bitcoin forum

Other

• MtGox Live Traders Forum
• Bitcoin StackExchange - Q&A site, currently in public beta
• Developer mailing list