We have an opensource code for a reverse bidding website similar to odesk. Some of the features do not work the way we want them to, they are non-user friendly. (As far as I can tell, it mostly uses the php framework codeigniter)
We want someone who will fix this, and change/edit the code to make the site interface much better; as good as odesk's is.
There will also be some rudimentary features we will need you to add.
We need similar development for multiple sites, so if you do this job well, there is plenty more work in the future.