Check out mintees.com or t-shirt contest sites like threadless and design by humans for artists.
You should find a designer that fits the style you want and contact them. Putting a job on a job board or doing an open submission for designers will not get you the best designers. Any designer who is any good is not going to waste his time applying for jobs they will already have enough clients contacting them.
You could get one of those artists to work on the logo but also there is 99 designs and logo design contests like that.
99 designs is good because you get a lot of ideas from designers and can pick the one you like the best