I spent the summer between junior and senior years of high school volunteering to help teach special ed students between the ages of 16 and 20 (or so) how to be independent. Except for two kids with aspergers who were basically normal the other kids were severely retarded (three of them were barely responsive) so there was no way they could ever be properly independent, just able to do a few basic household tasks to make it easier for their caretakers. Ultimately there wasn't much for me to do except sit and talk with them. The person in charge was a bitch and treated everyone like kindergartners (even the adult volunteers). All the volunteers resented her. So did the two near-normal kids, for that matter.
I was in Girl Scouts until middle school, but we barely volunteered. We sang Christmas carols to homeless people once, and at a nursing home (except that was really stupid because we walked up and down a hall once and then left). One time another girl and myself were volunteered by our troop leader to help a different troop one or two years younger than us learn how to do something related to a ceremony that involved flags, I think. I don't really remember because when we showed up the troop leader decided not to have us demonstrate because they had to learn to do it themselves, and she didn't want us to help with their other current project either. So we basically sat in a corner until their meeting ended and we got to go home too. Another time my whole troop was volunteered to help the youngest level of girls make chocolate-dipped bananas. This was more convenient for us since we were at the same location that day doing a different task for a different patch. It was the opposite of the other time the other girl and I "helped" because this time we all had to do everything for these girls. Except they got a patch for making chocolate-dipped bananas just by watching us and we didn't get anything related to helping them.
Currently I volunteer for "Friends of the Library", an independent group that sells books to raise money for the county library. They want to give everyone who offers to volunteer a task even when it's obvious they don't have any positions. So I stock the children's books for sale on a cart at the local library every other Friday. Stocking the cart is a one, maybe two person job, but there are at least four people (counting myself) who stock the cart. And the old lady who "trained" me couldn't even remember what she had just told me minutes before so I'm a touch worried that she might have not told me everything I needed to know. I think I'd rather stock books at the library since pricing and putting a few books on the cart doesn't take more than a half hour to do.