How can I find a sponsor for my social networking site?
The best thing you can do is generate traffic -- specifically traffic that increases month after month.
The next thing you can do is focus on getting targeted traffic, that is, making sure that the people who visit the site are also the people who would purchase from sponsors. Repeat visitors are really the key to growing your social network.
And, last, but not least, don't ignore growing your in-house e-mailing list. That's really important and something sponsors will want to know about before they cut a check.