I'd talk to your school's PTO president. I love the idea of helping in OUR community, or helping in OUR school or doing things that directly benefit MY kids before volunteering elsewhere.
When I asked the PTO president, she said OF COURSE they could use "at home help"! I now have two jobs that help at our school...I sharpen pencils for my child's 1st grade teacher (since I can't be in the classroom with a toddler in tow) and I help count soup/labels for education twice a year. My kids love helping me - because they know it's helping their school (what a great lesson!).
Both "jobs" aren't career builders, but they make a lot of difference to people at our school. There are often many "mindless" jobs like cutting, organizing, collating, etc. that your school needs help with.
If not, what about your local girl/boy scouts? I know we are always happy to have an extra set of hands planning our meeting, events and summer camps. Many of these jobs can be done at home, in spare time. (For example, right now planning us underway for GS Summer Day Camp for our area. There is a "food prep" Mom who is doing all the snack and meal planning, budgeting and logistics of how it will all be made. No small task, but critical for our summer daycampers.) It's ALL volunteer based. Without people like you, our kids would never get to GO to summer camp at all.
I highly recommend you think of something you can continue doing - like maybe helping Boy Scouts if you think it's something your son will be doing in the future. You have time to "learn the ropes" now, and can take on a bigger role later as your son gets older/more independent.
I know my kids LOVE telling their friends, "Hey, that's MY MOM!" Plus I think it teaches our kids that I am vested, interested and helping THEM.