Almost any platform you could want: XBMC has updated to version 9.04, codename Babylon, available now for Windows, Mac OS X, Linux, Apple TV, the classic Xbox, and bootable CDs or USB drives.
This update finalises features that were part of the 9.04 beta, including:
PPC (PowerPC) support for Mac OS X, VDPAU (NVIDIA GPU Hardware Accelerated Video Decoding for Linux), updated Codecs, new Karaoke features, more Media Info Scrapers, improved FanArt support, and of course enhancements to the XBMC Skinning Framework making it even more flexible and powerful.
Hit up the 9.04 changelog for a full look at the changes, or just head to the download page to grab the latest for your favoured platform. XBMC is a free download, works almost anywhere you could want it.