Metapuzzles are one of the more interesting recent trends in crosswords. They hadn't seen much action until about five years ago but nowadays many crossword constructors are populating their blogs with them. Even The New York Times features a metapuzzle every so often.
Metapuzzles are like regular crossword puzzles but with one key difference: when you're done solving there's a secondary 'puzzle-within-a-puzzle' that you need to tackle. This secondary puzzle is called the 'metapuzzle' (or simply 'the meta') and it's usually a single word or phrase such as a celebrity's name, a country or a movie title. Thanks to the 'Aha!' moment- the adrenaline rush that you get when you realize you've figured it out- solvers love metapuzzles.