I am on freelance career for around 1.5 years. From the very beginning, I started to like freelancer.com site. By this time, many things are changed(new attractive layout design, features addition etc). Here I will try to mention some features that make freelancer.com, a uniquely featured site for people finding freelance/outsourcing jobs online:
* COST : Most important feature is its costs. There are many types of cost that freelance service providers faces working online such as project fees taken when won a job, a percentage of earning/bid amount, withdrawal fee to a payment processor or bank account, percentage on bonus payments etc. freelancer.com is best about this according to my experience. they only cut 10% project fee on bid amount for standard member(3% for golden members). No percentage on bonus payment. Lowest rate as withdrawal fee($1 for paypal,moneybookers;No fee for debit MasterCard).
* Lots Of Projects : Its not exactly like unique features, its actually an advantage for freelancers. As this site is very popular and second highest score among freelancing/outsourcing sites at alexa, many projects are posted daily here. SO, its easy to get a job quicker also.
* Membership variation : This site offers you to use two different kinds of membership, standard and golden.standard membership is for those, who works less frequent, golden membership is for professional freelancer want a long term commitment with the site. And obviously golden members get some more facilities than standard members(lower project fees, more expertise, portfolio projects-newly added).
* Extra knowledge on projects bid : You can inquiry for more info either privately(through private message box), or publicly(project clarification message board). You can also become sure whether the project owner has the ability(amount on his account) to pay you for the full project(newly added features). Also, as like other sites, you can check the buyers reputation checking his previous feedback as service buyer.
* Dispute System : You can cancel a project after win if you can't synchronize with buyer's specifications for any kind of reason. Also, a project owner can't give you feedback until you get the full amount bid for the project. Moreover, for more complicated problems, they have dispute system, where you can submit an complain , submit proof & get justice.
* Verified Ratings : You will be rated by project owners only after you are being paid by them. So, no worry to get 'bad rating and no money'. If you can't agree with project owner, try to cancel the project, even if they don't agree to do so, they won't be able to do anything but an incomplete report, that actually have no effect on your overall average rating.
There may be a lot more advantages compared to other sites, but as I am not very old there and didn't experienced that much on other sites yet, may be i am not seeing those points. But, I will try to share my experience with this site much more times in future.