It really depends on how experienced you are and what the job is you are doing. If you don't have any professional programming experience you are looking at a lower number then someone with professional experience.
I usually look at my needs in terms of how much I need to make per month. Divide that number by 160 and you get your target hourly rate. Adjust it up or down depending on how you read the clients budget. Variables such as work load also play into your hourly rate. As you get busier you can quote higher.