I found this and thought it would be useful to show people:
http://freelanceswitch.com/rates/
It shows what you should be charging an hour, based upon your expenses and set up costs. I was astonished at what I should be charging and I don't think i would get away with $122/hour it suggested.
I wont say what I actually charge as it is not allowed on this forum, however I think it's worth checking this out as it just keeps your finances in check and makes your realise the overheads that need covering when you are working freelance.