The December 2006 CTP of WPF/E, a subset of WPF that can be downloaded as a ~1MB browser plug-in and will run in the browser was released yesterday for Windows and Mac OSX. Also released was an accompanying SDK. WPF/E (codenamed Jolt) was announced at the Mix06 conference and was scheduled for a first public release late this year. Kudos to the team for getting it out. Scott Guthrie has more details here, or you can visit the WPF/E developer center. Shawn Burke of atlas toolkit fame has a toolkit extender to simplify the inclusion of the right WPF/E client-side stuff. One notable omission from this release seems to be CLR support. One of the ambitious features touted for inclusion with WPF/E was a subset of the CLR, but as Doug notes it seems to be missing from this release.