The American Music Center has one of the most interesting web-radio stations I've found, playing a large range of music composed by Americans in the last century up to today. They have a small collection of archived pieces that I've also been listening to.
Here is an interesting interview-conversation between the multi-media artist-composer, Meredith Monk and Bjork, who I'd never really known anything about until listening to it. Meredith Monk has been a figure in the contemporary arts since the 60s. It's interesting to hear how much these two artists, from different generations have in common and how they interact. It's always a pleasure to hear young artists who have some sense of older artists.
I'd also recommend the short introduction to American Serialism. And The New Music Box is always worth looking at, even on those occasions when I don't agree with what some of their columnists say. This month has an interesting interview with the composer Bunita Marcus, who I didn't know about at all before reading it. Watch and listen to the video, it's extremely moving, hearing how she composes out of her experience of abuse. And here is a related article Hearing and Remembering Trauma in Bunita Marcus's The Rugmaker. If only I could find some of her music to listen to.