Ning and the sorts

Has anyone tried to build a social network around your web topics?

Ning.com seems to be a good choice. They host online community for free if you don't mind using subdomain. If you pay, you can use your own domain, pointing to Ning.com's host.

However, I don't think I can add html in Ning's network.

The alternative is kickapps.com

I think both services allow merging of online community with your existing web site through a process called DNS masking. So that even though Ning or Kickapps host your community, they appear at your web site under the same domain name (though through subdomain), i.e. community.yourdomain.com

If you have better ideas, let's discuss. :-)

Thanks.
CT