My friend Daniel DeCastro, talented composer and fellow atheist, finally has a web presence. He has two MySpace pages: his personal page and, most importantly, his music page with samples of his music! I've been hoping that he'd do this for a long time; and the samples include a movement from of his amazing Symphony #1 in progress. He's also writing a string quartet and a set of preludes (one in each key, like those of Bach, Chopin, or Rachmaninov), so when I'm talking to him about his composition I almost feel like I don't know what century I'm in—but his music also draws from the distinctly 21st century inspiration of video games and anime.
For another local composer's webpage, see that of Columbia University's Christopher Bailey, who among other things is the composer of dorkbot and artbots theme songs and has music online at his compositions and MP3s pages.