Hi vB forums support a referral system and you can use it to allow your users to invite friends. You can use this system to increase new registrations. Install this hack from vB.org - it allows your users to invite their Yahoo, MSN, GMail, AOL friends to join your forums. Next, install this addon which I developed. Once installed, it shows the latest referral on the forum homepage (just like on digg's old design). Check out this forum to get an idea. Try this on your forums and let me know if it helps.
I don't see anything on your forum that'll increase forum registrations or improve it. What features does your forum have?
it's got nothing to do with my forum. in fact, my forum is almost dead now. I left that project. I just wanted to show this useful addon to DPers who may need it. The link to the first hack is broken - heres the correct link - http://www.vbulletin.org/forum/showthread.php?t=145882
sunil, I checked your site but I don't see the example. Removed it perhaps? Have you personally used this? If so, how successful was it?