Technically the spin of an electron never changes, but the orientation of that spin can change: What exactly is the 'spin' of subatomic particles such as electrons and protons? Does it have any physical significance, analogous to the spin of a planet? | Scientific American
A longer explanation by science writer Chad Orzel: Electron Spin for Toddlers | ScienceBlogs
Since we currently believe electrons are point particles without physical size, “spin” is more of a quantum mechanical state than physical rotation about an axis. This video summarizes the history of how spin was discovered and how viewing it as physical rotation is misleading:
