just found this as well so the browser isnt out of the question
“I was messing around with the Media Extender interface on the X360, and noticed that the "More Programs" linked to a couple of apps installed on my PC as part of the Media Center Package, including MS Instant Messenger and some other stuff. All of these run when you access them from the 360 Media Extender client. The 360 essentially seems to act as a dumb terminal, interfacing with the application running on the PC.
Here's where things really get interesting: It's apparently very easy to integrate Windows applications into the MCE "More Programs" tab. All you have to do is build a link in a format specified by Microsoft and do some minor optimization, and the app will run in MCE. Here is how Microsoft describes the process of building games for MCE: msdn.microsoft.com.
So I downloaded a couple of apps and installed them on MCE, switched over to the 360, and lo and behold, most of them run perfectly. I was able to run apps with modified browsers to pull down news stories, stock quotes, sports scores etc., as well as several Internet Radio clients."