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Hi guys,
Out of the following,which forum software is most popular and what features makes it popular?
1.vBulletin
2.SMF
3.Invision Power Board
4.phpBB

vBulletin - tech support is pretty good, the application is very feature rich and the code is written fairly well which makes it very easy to extend and integrate new features.

In my opinion, phpBB is the best forum software. It's easy, full featured, very customizable, and very popular.