They've finally released a soundtrack album with all of the great original songs used on the show. "Let's Go to the Mall," "Sandcastles in the Sand," "Nothin' Suits Me Like a Suit" and "You Just Got Slapped" are all included.

How I Met Your Music is available on iTunes:
http://itunes.apple.com/us/album/how-i-met-your-music/id562393536