I do freelance coding work in my spare time and try and combine it with some open source stuff too as a way of boosting my web presence. I recently made £500 in a month doing work in my spare time, not a huge amount but add on a full time job, it's nice to have the extra income.
Link to my latest project - https://github.com/DrRoach/DynamicImage (It's a dynamic image generation library if you're interested)