In preparation for the debut of Design Squad (which I have discussed before), WGBH will be hosting a training session for engineers in November in Washington, DC (as well as other sessions around the country). Getting volunteers, especially STEM professionals, into after-school programs is a big challenge. It is also very important, given the importance of role models in career choices.
Developing a strong volunteer base for after-school is something that must be done deliberately. After-school leaders need a consistent commitment, and scientists and engineers want to feel like their unique skills are helpful to the program. This usually happens with a local connection and often with an intermediary, such as a museum. (WGBH has developed partnerships with several engineering professional groups.) FIRST Robotics is a good example of a group that has standardized a practice for recruiting volunteers in support of its local chapters.
As for individuals, here are the thoughts of a scientist preparing to volunteer his time with high school students.
If you have other examples of strong volunteer programs, please share them with me.