Ask YC: Where to find a movie, restaurant, music or hotel database?

I'm wondering if anyone has found or licensed for commercial purposes a good data set for movies (e.g., IMDB, allmovies), restaurants (e.g., infoUSA, yellowpages?), music (e.g., allmusic), hotels, or any other area where you might want a reference file with item names and details.

Whose data sets were good and bad? What terms could you negotiate?