Crunchbase seems like a good start, but I'm not sure how up-to-date the list is http://www.crunchbase.com/company/y-combinator http://www.crunchbase.com/compan

Crunchbase seems like a good start, but I'm not sure how up-to-date the list is http://www.crunchbase.com/company/y-combinator http://www.crunchbase.com/company/y-combinator