Not everyone likes the ODesk model but it is worth mentioning if you prefer to be paid by the hour rather than per piece or per job. If you fall into this section of the freelance job market online, ODesk could work for you.
The site promotes transparency between providers and buyers, by asking the providers to download software that allows the buyers to watch them while they work. Every time you sit down to work on your tasks, you will know that the buyer can see what you are doing. Not everyone likes this way of working but if you want to work with ODesk you need to know this is how it is done.
If you are being paid by the hour and you are used to working in an office environment, you will probably get on quite well with ODesk. Freelancers who charge by the job do not tend to like it, because it means they have to allocate specific blocks of time to their freelancing for a particular client. This may not work well for you, and it does take away some of the spontaneity about working from home.
In short, if you want to give ODesk a try, make sure you read through all the information the site gives you about how things work. If you are happy with the procedure you could find a lot of clients via the site. If not, there are lots of other freelance sites to try.