Have you been able to use your software engineering abilities for charity? If so, how did you find the opportunity, and what effect were you able to have?
I recommend you just get involved in whatever charity interests you and, after establishing connections, let them know you have X, y and z expertise to bring to the table.
Some super model began showing up at some program and was doing really menial tasks, like serving food in a soup kitchen. She wasn't there long before big wigs jumped on asking her to be the face of their PR campaign.
If you are humble, willing to support their cause and you have unusual assets they don't often see, most charities will jump on that just as soon as they understand what you have to offer.
Local conservation or biology groups like that typically have a lot of data but not many people with the skills to organize and analyze it. They're usually pretty grateful to people that can help with that.