Transcode 360 v1.0 Beta - Runtime (you might remember him as the co-founder of XboxMediaCenter) has created Transcode 360, a new tool for Xbox 360 and Windows MediaCenter he released today:
Designed for Windows XP Media Center Edition 2005 and the Xbox 360, Transcode 360 aims to broaden the support for a wide range of video media including DivX and XviD. - www.runtime360.com
The underlying mechanism for transcoding and streaming is much the same as /mceDivX360 however the user-interface is more tightly integrated with Windows Media Center, and generally more robust and easy to use.
The installation is pretty straightforward, it's all automated. If you run into any problems have a quick read through the included manual, the sections on optimization and troubleshooting are well worth reading.
The software runs in the background as an NT service, and with a few tweaks you can even shift the burden of transcoding to a more powerful computer on your home network. Looking forward we have plans to replace Windows Media Encoder with an open-source transcoder that will be a) less CPU intensive b) more compatible with an even wider range of codecs.
The project will be open-sourced under the GPL license once Subversion hosting has been provisioned.
I found this article on streaming DivX Video through your PC to your Xbox 360.
"Quote" - This article shows how to stream DivX (and XviD) movies to an XBox 360 using a Media Center. for the picky people, it doesn't actually stream DivX ... it converts to WMV on the fly to stream. the core process for accomplishing this is taken from a thread found on the XBox forums : Playing DivX movies without having to Re-encode, through media centre. this works fine, but has the disadvantage that you have to manually set up the encoding process on your Media Center and then move over to the XBox 360 to watch it. so all this article really does is provide an MCE interface so you can control everything from your XBox 360 being used as an MCE Extender. i.e. its for lazy people. "Unquote"
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.