There are tons of different Freelance jobs available. Some of the positions you may have heard of are freelance write, data entry, translator, logo design, and tons more.
Basically this is just like being a independent contractor offline, where you get paid on a per job basis. If you do a good job you may land a long term relationship/contract with a client that can give you full time work, but there is no guarantee.
Personally I do a bit of freelance work in my spare time, but I use Fiverr. The more popular sites are Elance and oDesk.
