There are sites (I don't recall them off the top of my head) that allow you to request bids or you could advertise on sites like craigslist for your local area. If you knew what technical skills you need then the ad could be more generic, but again, at some point, you'll need to describe the details. Details are required so that the person responding can give a calculation of time required to do the project, and therefore cost expectations. Odds are they will first want to properly spec out the project which also shouldn't be free.
Is your idea so unique that you think someone will spend most of their waking hours trying to beat you to delivery? Most programmers are busy trying to make a living and side tracking onto other projects is very expensive in time and costly to ignore making an income. Oh, and if you idea is so hot, when it is released, others will jump on this great new awesome bandwagon an try to duplicate the idea.
Do you have a great deal of money? Development is very costly. To get a basic idea implemented with no bells or whistles could be around USD$10,000. Also, get a good lawyer who deals in contract law and specifically understands software development requirements. For instance, you could end up with a product but no rights to the source code!
You'll hear many people say ideas are a dime a dozen. The reason is simple enough; Implementation of the idea is required to make an idea worth something. Since you are incapable of implementing the idea, you are going to have contract, pay, and trust others.
Good luck with the venture.
