How can a software developer best volunteer to help childhood cancer research?
I work in a biomedical field and most of us are awful programmers. We tend to be more interested in getting the underlying back-end algorithm to work than worrying about the front-end, comments, documentation, version control, unit tests, etc.

My suggestion, would be to look through the web pages at a nearby university and see if you can identify someone doing something you think is interesting, preferably something computational. Then email the PI explaining your skills and experience and that you would like to volunteer to help people with their programming and that you could help people move to the next level of using tools like version control and work with them on documentation and the front end.