This afternoon I updated the version of Xbox Media Center that was installed on my hacked Xbox. If you recall, I installed most everything using Slayer's AutoInstaller, which works great for getting you up and going quickly.
Xbox Media Center allows you to access all of your MP3 and WMA files on your Xbox HD as well as your Windows Network. You can also play music from iTunes and Shoutcast servers. Not only music is available on XBMC, you can also use it for slideshows (which I've done with our honeymoon pics) and for playing movies (DVDs and video files like .mpg, .avi and .wmv). The older version had all of these features, but one of the new features is the ability to change RSS feeds to receive the latest news headlines. Slashdot and Yahoo news headlines can be accessed like this.
The kicker for me was the ability to have Milkdrop for visualizations for the music. The default visualizations for MP3s and the like was your average run-of-the-mill blurred oscilliscopes and spectrum analyzers. Milkdrop adds a virtually limitless array of plugins to allow for any mix of visualization plugins. The new version also features an improved web-interface to control music/video playback on the Xbox. Couple all these new features with the Xbox remote control and the enhanced audio adapter to allow for Dolby/DTS output and you've got a setup that rivals most any homebrew home theater PC setup.
update: After installing XBMC I found a few additional scripts that are very handy. My favorites that I have installed are XMovieGuide, which shows movie times at area theaters; XRadar, shows local area weather radar; and the 'PBS Frontline script', to view the streaming video archives of the television show "Frontline" on the Xbox.