The beta of WPF 3.5 SP1 is now live. This is way more than a service release, even if it's named as such. there are more new WPF features between 3.5 -> SP1 than there were between 3.0 -> 3.5.
The best all-up run-down of all the features (WPF, ASP.NET, WinForms, VS etc.) can as ever be found on Scott Guthrie's blog:
TIMS has written a pretty comprehensive write-up of the WPF-specific features here:
Brad Abrams posted a ton of screenshots of the various features:
Check it out – there’s a lot to be excited about here. With this release, WPF really starts to move into the mainstream.