I installed the Yougle Vista plug-in a few weeks back and it's an OK plug-in for getting some online media content in to your Media Center.
"Yougle Vista allows you to watch community video - at the moment, video from YouTube, Google Video, DivX Stage 6, DailyMotion, WWITV, music from Shoutcast and (for Australians) The Chasers War on Everything and pictures from Flickr and ICanHasCheezburger - from the comfort of your own lounge, via Vista Media Center."
Yougle Home Page
I was able to watch You Tube video's, which took much longer to load and play than in the IE browser. Look at photograph's from FlickR and listen to some Internet radio stations from Shoutcast.
The reason I say it's an OK plug-in is I found the UI a bit clunky and the menu systems a little tricky to control. Also there where video and audio sources present for Ian Dixon's Media Center show, but when trying to add these it came up with an error and did not work. I think Yougle needs some more work to make it slicker but it is worth trying it out however and I would recommend you take a look at it.