I'll second this. I routinely counsel clients to plan on spending 75/hr for a junior to mid level developer if they want someone competent, 100-110/hr for someone senior level, and 125-150/hr if they're trying to roll multiple skill sets into a single contractor or firm.
The biggest mistake you can make as a contractor is underpricing yourself. Not only does it hurt the market but you can find yourself in situations where you can't work enough hours to cover taxes, downtime, benefits like health insurance, much less a vacation. Then you start making mistakes like overbooking yourself to make up the difference and do a crappy job with all of your projects.
When I was consulting we charged 125 an hour for any small jobs, like less than two work weeks. The problem with small jobs is that the overhead from meetings, paperwork, phone calls, design, server setup, etc is routinely more than the time it takes to actually write the software.
