Getting stuck into an open source image processing/computer vision project I have a degree in Electrical Engineering (focusing on VLSI). However, I am more mathematically minded, and only recently discovered that image processing seems to contain lots of interesting maths. I am looking to break into this field in a about a year or so in spite of not having any formal experience in this area. 

I was wondering: would contributing to code development on one of the open source projects help my cause? Would this enable me to overcome my lack of formal education or experience in this field? 

I would also appreciate it if someone could point me to good open source resources. I know of GitHub and Nasa's Vision workbench. However, I have not contributed to any open source projects and I don't know what to expect.
I believe it would if you intend to practice your knowledge, rather than go into academia.

I suggest you look into the code base of opencv, simplecv, and scikit-image, as suggested. Once you become comfortable with using them, you can submit patches for bugs and new algorithms.

Nevertheless, you will also need to understand what you are doing at a theoretical level, so get some books too. There are also courses online, such as this and that.

Good luck!