I will only side with 4 freelance websites when I look for outsourcing my landing pages and websites that I use to run affiliate offers. They consist of:
Elance.com
Getafreelancer.com
Guru.com
yourmaninindia.com
Unless my projects concern a specialized job, I usually rely on these four main sites alone.
These are the places I rely on heavily the most, and the place where you should start building your team of contacts with. It is good to explore more than one website, as each one usually attract different sorts of freelancers. So by hanging around at different ones, you can enjoy more diversity in the talent pool for your company. Out of the freelance sites, elance.com and guru.com are the most professional and have the most diversity for online . The freelancers there are more dedicated and have a better working experience. If you are just starting off, then by all means start off from there.
You will have to pay a higher price too. Prices on getafreelancer.com are much lower, but it has fewer options and is more informal in its nature. Freelancers who like to work proper with professionalism and work code prefer elance.com, while those who want a freer, less strained environment stay on getafreelancer.com. This is also the site to use if you ever want cheaper work, since most workers here are from foreign countries. Yourmaninindia.com is very specialized and will handle mainly tasks that you need. It's good to be creative with them, as it makes everything easier on yourself.
The trick is to choose websites on your list, and depending on the type and budget of your project, prefer either one for posting: if it is important or requires top notch professionalism, like most on-going procedural tasks, post on elance.com; if it is less critical and do not require strict procedures, like website building or article writing, go for getafreelancer.com.