After years of planning to practice our Spanish and barely doing so, my husband and I are in Ecuador for a few weeks taking Spanish lessons. One-on-one conversation is way better than books or group classes, and the fact that we pay for regularly scheduled sessions means we actually spend 4 hours a day at it. Other than the money spent, it's entirely painless (unlike practicing at home, which felt like a chore).

The going to another country part isn't really necessary. I'm sure there are similar services at home, but this way we combine vacation with gaining a useful skill.