Many of the volunteer activities I do involve putting out mailings -- some small, some larger. I've been gradually converting these mailings to mail merges instead of using stick-on labels. It's easier not to have to sticker the envelopes, and it lets me add personal notes to the letters I'm sending out without having a whole separate document (or worse, writing it out by hand).
I've been looking at this effort as a long-term investment -- the effort of building a database has been more than the amount I save on just one mailing, but future mailings are much easier.
But as I do this more and more, and get better at it, I find that now the effort pays for itself in just one mailing. Hooray for the Right Tool For The Job!