What Themes and plugins do you recommend for Membership Site

I am somewhat familiar with wordpress. I have set up my host as a wordpress Multi site.

I am creating a membership site that is going to contain several different blogs, a article and ebook training area, video area, store, latest news, social networking, photo sharing.

I don’t want the members to have to sign in as they go to the different pages, just once with the membership plugin.

Can you please recommend the best theme to use and plugins.