I am willing to bet that your local Public Library would be most welcoming to the concept of pro-bono tech support for their most likely ageing/not updated/not virus protected public computer terminals as well as some TLC for their network infrastructure. Many Public Libraries have been forced drastically scale back their services to the public. Offering up your time to help them keep their systems running/patched/protected and their network functional would be a huge help to them.

I have, over the past ten years, helped the Public Library in my home town, set up 10 new publically accessible internet/work (office and other productivity programs) terminals (Mix of Dells), a youth computing room (Apple Mac Minis), new staff computers (Dells), as well as help educate them on how to maintain, patch, update, and create regular ghost images of the systems to allow for restores. Not only are they grateful, but the people of my home town are happy because they have one of the most technologically sound libraries in the surrounding area. It didn't take a lot of work, but has been immensely rewarding.