I have money direct deposited into my vacation fund at the Credit Union. All my change goes into a jar. And I just bought a big hard plastic piggy bank at the dollar store. It doesn't have a plug in it, so the only way to get the money out will be to cut a hole in it. That's where any extra cash will go (overtime, tax rebate, etc.) Once a trip is booked, usually about 4-6 months out, I do the Disney gift card thing on every trip to the mall. If you take it in little bites, it's a whole lot easier to swallow.
I'm considering taking my great niece-6 & nephew-9 down around this time next year (my niece is a single mom and has NO extra money.) I took two of the containers the Crystal Light tubs come in, cut a slot in the lid and glued the lid to the container. I'll let them decorate with some Disney stickers, and they can start savings their own spending money.