there is one nursery I go to that I've seen volunteers at. I would volunteer there now that I know the owner's health is on the decline. I'd be interested to see what the answers are.
I know they take volunteers at AOS, but I only see them giving tours, not working with the plants. I could have just missed them.
Good question--would be a great way to hone potting skills, become more confident, etc. for new growers.