As a subscriber to Sirius Satellite Radio one of my favorite new applications for Mac OS X is StarLight from NiceMac LLC.
It's a super simple, thin client to access the Sirius radio Web streams. Currently at version 109.a (download link) it's an excellent alternative to Sirius' hokey Web interface which requires a login (with captcha), WMV components for QuickTime and can't be paused. Worst of all, Sirius Web streaming doesn't work with FireFox on the Mac.
Just fire up StarLight and choose a station from the drop-down list, it's simple, fast and a breath of fresh air compared to the Web interface. Even cooler is word that NiceMac is hard at work developing a Sirius app for the iPhone. I can't wait.