It depends, you can sign up to many different freelance job websites such as freelancer, elance or peopleperhour.
If you are looking for a site to post a job with no registration/verification/hassle then take a look at http://facingworlds.co.uk it is a free and open job board I found recently, pretty cool for picking up odd dev/design jobs.
If you are looking for a site to post a job with no registration/verification/hassle then take a look at http://facingworlds.co.uk it is a free and open job board I found recently, pretty cool for picking up odd dev/design jobs.