Thanks to The Green Button, I just found two more cool applications for Media Center 2005:

mceWeather: Shows your current weather, forecast and sattelite-image of your city on your tv!

mceContacts: Now you have all your contacts, adresses, telephone-numbers right on your TV or monitor. Supports import from Outlook but I can't vouch for how well.

It's great to see more developers writing apps for Media Center.  Let me know if you come across any cool apps as well.