One of the participants in our last workshop suggested Fiverr.com as a place to get logos (and many other things, like translations and gifts) for cheap. For $5 in fact.
With any program like this, watch out for copyright violations. Although the Fiverr terms of service explicitly says that sellers cannot offer material belonging to others (images, logos, code), some sellers may violate the terms and bad things get through.
If you’re not sure about an image or logo you bought, use Google Images to check. Report any violations to Fiverr’s customer service department.