There are similar (some of them better) alternatives, the problem is that once you have a good history/reputation on one of these sites you can't transfer this to another one. You start from zero.
I kinda dig oDesk. I got many decent clients off it. I was shooting for small, very short term projects - the kind that can be done within a day - so YMMV.
This very site's monthly freelancer thread is also worth checking out. I got a few decent leads out of it.
