Today I discovered the Sirius plugin for Firefox. It's truly a wonderful thing. It runs in the background, not requiring a window to stay open. You click "Sirius" at the top, select a channel, and away you go. I am using it in FireFox 3.0 with no issues whatsoever.

If you are a Sirius listener I highly advise this plugin. Simply go to https://addons.mozilla.org/en-US/firefox/addon/3546

Enjoy!