for creating site like boddunan you have a complete knowledge of asp.net.
Anyway, here are my suggestions apart from all others said:
1. Learn web programming
2. Set goals for what you want to acheive
3. Plan for the things you want to do over the time
4. Have loads of patience, Boddunan is 2 year old project ;)
5. Have plenty of cash ready
And finally more importantly, keep motivated. Good luck.
When opportunity is in front of you, don't hesitate to catch it. It will never come to you again. - Maverick
Sumit, I exactly don't know what you mean by site like Boddunan. However like boddunan, if you want a user generated content site with a dedicated forum, it is pretty much easy and would hardly take you 2 full days to setup. Though it will cost you some money but not much.