Trailers are such an important part of the marketing of a movie, and the choice of music that is used in the trailer is equally as important. Best thing about it for me is hearing as little as 20 seconds of the song used in a trailer and thinking "Wow...I must find out who plays that", which leads to finding new bands.
Here's a short list of music that has featured in trailers recently that I have found new music to listen to from.
"Snow Patrol - The Lightning Strike" is featured in Dreamworks "Epic" trailer as well as "Act of Valor"
"Florence + the Machine - Seven Devils" was featured in the season 2 trailer for HBO's "Game of Thrones"
"Imagine Dragons - Radioactive" is featured in the latest trailer for "The Host"
"Nico Vega - Beast" was featured in the latest trailer for "Bioshock Infinite"