Disclaimer: I haven’t used these resources directly, but I have heard positive things second- and third-hand from colleagues and online reviews.
If you need some contract graphic design help—specifically around logo design or branding—then check out the crowdsource sites CrowdSpring, 99Designs, and DesignCrowd. CrowdSpring was the first that I’d ever heard of, and probably the one I would initially check out. However this guy thinks 99Designs is the way to go.
The basic idea is that you post a project with scope, requirements, and budget. Then designers from the site will pitch ideas to you. You can iterate a bit with them, then choose the one you like and get that one polished up and delivered to you as high-resolution assets. Here’s a logo example from one of the sites:
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