[logn]

Whatever you're looking for you won't find it on Elance or similar sites. Generally, those are places to pump out boring work at cheap prices.

As far as skills go, just look for programming skills, ideally with a body of completed prior projects. Hopefully the projects are somewhat large and/or complex (not a GitHub profile with a few forked repos and toy projects). Of course, many good developers have no publicly available projects but as a non-technical person you will have a hard time judging those people and they're probably not the type to work with you anyhow (they want benefits and paid vacation).

I'd recommend something like Craigslist - Computer Gigs or if you want to pay someone market rates, Craigslist - Internet Engineers or Stack Overflow Careers.

Also, if you are paying market rates, you should reframe how you're explaining this. The gal/guy with an idea in search of a coder on Elance is a pretty poor first impression. Just say you're a bootstrapped/self-funded startup. And make sure to do your share of the business side of things which somehow most non-technical people aren't actually good at. Line up paying customers rather than taking a Field of Dreams approach.