A list of popular outsourcing sites
elance
rentacoder
getafreelancer
getacoder
odesk
freelancerchina
sologig
guru
Drupalancers

some discussion on these sites

LinkedIn also has many very useful discussion on using these sites.

Here is a nice article on "How to use elance/rentacoder/guru Outsourcing Sites"

This list is by no means to be complete. I know there are many other similar sites. But rentacoder and elance seems to be the two most popular ones. What's your experience with these sites as a buyer or a seller?