Useful sites for forums

Value Investor's ClubInvesting ideas from financial professionals with a focus on fundamental analysis of small to mid-cap equities
SumZeroInvesting ideas from financial professionals and market updates
Corner of Berkshire and FairfaxOpen forum for discussion, equity-focused investing ideas from a wide range of people
Upgrade CapitalVirtual trading platform, forum for discussion with other Ivy League students
Distressed Debt Investors ClubInvesting ideas from financial professionals with a focus on distressed debt and equity opportunities
Reddit Security Analysis ThreadOpen forum for discussion, decent place to access books, presentations and other resources that are not readily available
TheLionSite that allows you to search for a stock ticker or a topic across multiple forums and commenting platforms