Now that WPF has officially shipped, we're starting to see some of our third-party vendors release their new or updated controls. I try to maintain a current list of WPF Tools and Controls, but I'm sure that there are others out there that I'm simply not aware of (drop me an e-mail if you know about something I've missed).
First, DevComponents has announced their Wpf-Ribbon control. The control is currently in private beta, but you can sign-up to be notified when the public release is ready. Denis Basaric mentions that their control will offer complete support for the Office 2007 UI Design Guidelines. Based on their impressive DotNetBar for Windows Forms, I can't wait to see how their WPF version turns out.
Second, our good friends at Infragistics have announced the public release of NetAdvantage for WPF 2007 Volume 1 – Beta 1, a bundle of WPF controls that includes: xamDataGrid, xamCarouselPanel, xamCarouselListBox, xamDataCarousel, xamDataPresenter, xamEditors, some StylePacks, and the cleverly named xamples Browser. Although I'm not up on my 13375p34k, I think the last one is a Samples Browser (am I showing my age?). :-)
Infragistics has some deep history with Avalon/WPF. If you attended the PDC in 2003, you'll remember a very early demo that was shown during one of the keynotes, and they have been featured in many demos since (including at the Windows Vista launch events). I've been working with Infragistics for over two years now, and they've put a lot of good thought into their WPF architecture. You should check out their stuff.