WordPress MU

Is there any way to make Individual Admin Site for each Authors so that they are able to see and edit just their own posts and comments?

I'm hoping you are asking a simple question: http://codex.wordpress.org/Roles_and_Capabilities#Author

Check the list of Users for that blog and change each user role to Author - an Author can see and edit only their own posts.

If you want a single "super Author blog" to edit all an Author's posts collected from any number of blogs, that is much tougher.

I think I want simple thing and as I understand it supposed to be like that but I made a few users with Author's role and on each of their Admin Site I can see ALL post from ALL Authors. Authors are not able to edit posts of others but but they can see them on their Admin Site.. So is there any way to fix that?

I have a wpmu install and want to create blogs by subject and allow people to add posts to these blogs without going through a sign-up process which involves blog admin.
Is there any plugin available to achieve this.

@kavitamm: try tdoforms plugin from thedeadone.net and please don't go hijacking threads, open your own one :-)

Thanks Ovidiu, will try this plugin and remember your advice for opening new thread next time.