If it were 2004 maybe this would require some thought. In 2012 it requires none at all. Start putting out some feelers for jobs. Take some interviews. When you've got an offer that looks more promising, give them an amount of notice that shows you care about them and cut your losses. Offer to help with the transition to contractors or whatever they want to do next.

You'll be able to save the relationships if you remain professional and polite and give them adequate notice.

It wont be 2012 forever. Demand for people with your skills is insane right now - don't waste your time. Get moving.

And next time you agree to be a technical co-founder (which is what you are here), be sure you team up with people who give you an equal say in the decision making process - not people who view you as an order taker.