The third major update of WPF has just been released as a Beta, as part of the .Net Framework 3.5 Service Pack 1 Beta. Here's a few links to blogs that have more detail:

Scott’s Blog [VP]

Soma’s Blog [VP]

Tim Sneath’s Blog [Dev Evangelist]

Greg Schecter’s Blog [Architect]

Jossef Goldberg's Blog [PM] (more detailed breakdown of features per area)

Vincent Sibal's Blog [SDET]

Channel 9 WPF Intro on SP1