@KoiwiGal - Teaching English to people is actually a fairly good skill to have as well, for work opportunities and just as a general skill that can help you to relate better to everyone.
I'm a bit selfish when it comes to volunteering, I have to admit. I'll often only do it because it comes with some kind of really awesome opportunity.
For example, they had a tree planting volunteer opportunity on a local island recently and I had a lot of fun doing that. I would never have been able to afford to go to the island under my own steam, but they shipped us over for free since we agreed to plant all the trees. Yes, it was a bit of work, but the experience was worth it.