1) Although being too secretive about a project isn't usually a good thing, I don't really want to plaster my idea on a site, either.
2) I think another (more controversial) approach to solving the 'co-founder problem' would be to create a database of users populated with answers to questions similar to the YC application form. So, one could filter based on interest level, availability, proximity, etc. Real names would be optional (news.yc user names could be used instead). Think YCombinator meets LinkedIn.
The more I write about 2), the more I like it. If I weren't working on another project, I'd implement this myself. In any case, contact me if you want more ideas (see my profile).