I need to create a leaderboard for a online quiz that I am about to conduct....
I also need to setup a login and a seperate forum for users in the same level to interact with each other...and I should moderate their comments... pls helpme..
Well clearly this is something you need to actually think about doing.
Do you know EXACTLY what you want to craete?
You have a lot of components/requirements there. Maybe think about it and divide them down into individual parts. Research it (if you want a forum, google: forums) and make sure you do know what you want and if there are any resources or similar items out there that might be able to help you through the process. Common forum suites (like phpBB) have these moderation filters built in.
Do you want to write it yourself?
If yes, which language do you want to write it in? Something like PHP/ASP.NET, but even then you need skills and patience. Start at one small point and grow it. If anything, get to know the basics of a language, and then maybe move to a framework for producing a proper app clients will use (for safety).
Does it need to be done immediately?
If yes, dont bother. Those who could produce this quickly, wouldn't be asking for help. Those wanting to learn gradually, wouldn't have a time scale.
The point is, you have a lot of things you want doing here. I think you need to sit with good old pen and paper and be sure you know exactly what you want and where you want to start.