New Music from the US
From WGBH, here's a directory of a variety of pieces from American composers that you can download and play. The only downside is that they're in RealPlayer format instead of mp3. It's nowhere near complete, but it is an eclectic sampling from composers as varied as John Adams, Robert Ashley, Milton Babbitt, Burt Bacharach, John Cage, Aaron Copland, Charles Ives, Steve Reich, Terry Riley, and Edgard Varese (among others). They have one of my favorite modern pieces, Riley's In C
, which I highly recommend if you are fond of minimalist music.