This thread may be old but I figured, people might still be coming across this post so here's my take:

I've known a few who went with Distilled and 97th floor and were satisfied with them. Both SEO providers mentioned are on Moz's recommended list which were also stated by the rest.

Now if you are really looking for a legit freelance SEO to work for you alone, you can try James of search marketing pro. Though they seem to cater to Australia only. But it is best if you ask (I mean no harm in asking, right?). I had an old website done with them and it was all good. A bugger as I had to close shop, though.

Odesk, which is now Upwork is generally better as it is now more like a real hiring process for the employer and the freelancer (It was used to be a horrendous bidding process with a lot of freelancers from developing countries outbidding the rest of the community bec. of low labor rates). I'm sure most of them are qualified to do the job. But look for someone who is really committed to work for you!

Cheers and happy hunting!