can u help me??

[kerthivasan]

i want to start a web site that allows all the users to enter post just like digit forum.

it should be free

[shivkumar]

Well try these
http://www.phpbbweb.com/
http://www.forumforfree.com/
http://www.jconserv.net/
http://www.forumhoster.com/
http://www.freeforumworld.com/
http://www.forumsplace.com/

Many website offer free web hosting with cPanel or cPanel-alike, you can use them as well most of them provide forum hosting.
Some of them are
http://www.frihost.com
http://www.qualisar.com
http://www.ifastnet.com - I have hosted a website with forum on this. They provide 350 MB space with 30 GB monthly traffic and lots of other cool utilities using cPanel-alike. Try it out.