Second I'll let you know that this is actually incredibly difficult. Generally speaking NPO (503Cs)aren't set up for technical volunteering. so you will have to search a little. They generally default to paying consultants mainly due to just a complete lack of familiarity.
Here's a couple of strategies:
- find a charity that you are interested in volunteering to. Charity Navigator keeps tabs on them and you can find a charity that fits what you are looking for. Email them and hopefully they will contact you about helping.
- Reach out to whatever University is in the area. The computer science department will often get requests for help with pro-bono projects... they can probably put you in touch with the right person/ project.
- Open source! Don't forget about open source projects. they need love too
- Organize Charity hackathons and get people together (Here's one we ran that was enjoyably successful: https://www.meetup.com/IPAs-and-APIs/events/249340851/)
and lastly if you want to give us a hand we'd love some help (https://github.com/jppope/academic-intervention ). We're working on a project to help reproducibility and open access in science. We work on the project every Thursday night after work. We have a couple of PhD candidates advising and a small team of coders working on the build.
Hopefully these suggestions help! I've had similar problems trying to give my time and technical skills away for a good cause, so I feel your challenge.