An Internet forum, or message board, is a bulletin board system in the form of a discussion site.he members submit topics for discussion (known as threads) and communicate with each other using publicly visible messages (referred to as posts) or private messaging.Take a look at the sample forum if you are new to the concept
You find a lot of forums written in php(pre hypertext processor) language,but there are some asp.net alternatives also available.The most famous and widely used among the php forum's are phpbb and vbulletin board.
Since its creation in 2000, phpBB™ has become the most widely used Open Source forum solution. Like its predecessors, phpBB™ 3.0 “Olympus” has an easy to use administration panel and a user friendly installation process, which allows you to have a forum set up in minutes.
With a large and highly customisable set of key features coupled with a standards compliant interface, phpBB™ will grow with, and complement your website. With millions of installations worldwide, it is no wonder phpBB™ is one of the most popular ways to create and support a community.The current stable release of phbb is 3.02 version which is availble for download in their homepage.The administrator panel looks like this
PunBB is a fast and lightweight PHP-powered discussion board. It is released under the GNU General Public License. Its primary goals are to be faster, smaller and less graphically intensive as compared to other discussion boards. PunBB has fewer features than similar software, but is generally faster and outputs smaller, semantically correct XHTML and CSS compliant pages.
Currently, PunBB runs on a number of operating systems that are able to support the PHP scripting language. To store its data, PunBB relies on either MySQL, PostgreSQL or SQLite.
list of available alternatives written in php and their comparison of features
list of availble alternatives written in ASP and their comparison