I hate to be "that guy" but seriously... this question (or some variant of it) seems to come up about once every 2 days or so. Have you searched for older threads on this topic?

http://www.google.com/search?hl=en&q=site%3Anews.ycombin...

http://www.google.com/search?hl=en&q=site%3Anews.ycombin...

There's also discussion of this on Quora:

http://www.quora.com/What-is-the-best-way-to-find-a-cofounde...

http://www.quora.com/What-is-the-best-ways-to-find-partners-...