There is a lot of programs for windows vista media center. below are some i have testet.
Program for showing wetherforcast in media center. Link
Greate program for controlling the media center guide and sharing the content from the mediacenter to other computers. Link
SystemMonitor for Vista media center
A system monitor. Makes it posibel for you to see the tmp and rpm for you motherboard in the media center.
Requers speedFan. Link
Tool for removing commercials from recordings. Skipping of commercials when showing. Link
Enables showing of online content: Music, Movie Trailers and more. Link
AOL for Media Center
AOL services for media center. A lot of free radios, Music Movies, Picture sharing and More movies comming soon. Link