I volunteered at the zoo for many years. It was physically taxing and you reeked at the end of the day, but it was fascinating to work so closely with animals most will only ever see from a distance or in pictures. Plus I could smoke.
You have to be able to pass a TB test. May have to have a vaccination for it now. Also, there is the whole pesky "if you're maimed, dismembered, or killed, it's on you" bit.
There are lots of opportunities if you're needing things with more flexibility. With kids now I'm limited to church and community events where they can either come and help, the bulk of the work is done at home or my DH is about to leave them with. Dinners, fundraisers, clothing drives, clean-ups, etc.
If you have a car, many communities have a need for drivers to either deliver things, run errands for and/or visit with people unable to get out. Or to transport people to Dr visits, church, grocery store or wherever.