Pond5

I am an artist contributor (ErickMcNerney) and have nothing but great things to say about them. When I started it took a few months to get my first sale, but after months of contributing, sale continue to increase and it doesn't appear that it will slow down. Their submission process is extremely smooth as well, and they have just about the easiest, most user friendly process. You can create templates and save them for future work that is very similar. It saves a lot of time. Although I do not want to bash on Audiojungle.net, but comparatively, the process is much better. They also review the work almost always the next day. My sales have also been steadier at Pond5, even through all of the ups and downs of the markets, it still remains steady for the most part. Don't waste your time and money on sites like freelancer.com. It's completely free to submit to Pond5 and other sites like these. If you're lucky you might get a trending track and make some good money.
My only complaint with Pond5 is that it seems that they accept a lot of stuff which is not the greatest quality.