Forum

https://en.wikipedia.org/wiki/Forum

List
http://forumlist.info/

Biggest
http://www.thebiggestboards.com/

Create
http://www.createaforum.com/
http://www.forumotion.com/

Top 10
http://www.moreofit.com/similar-to/www.big-boards.com/Top_10_Sites_Like_Big-boards/

Tube
https://www.youtube.com/results?search_query=forum

Slides
http://www.slideshare.net/search/slideshow?searchfrom=header&q=forum