Most distributions ship with Xfce in their own packaging format, but if you want a newer version or you want to build Xfce from scratch, you can find the packages below. Instructions how to compile Xfce can be found here.
Stable release 4.12
Xfce 4.12 is the most recent version of the Xfce desktop environment. You can find the changes in this release here.
Each package in Xfce can make individual stable or development releases, including the core packages (as described in the release model). You can follow the announcements of the releases on the Xfce users mailing list, watch the release feeds or follow the Xfce identi.ca channel.
A lot of different distributions provide Xfce packages. Popular examples build around Xfce are Xubuntu, the Fedora Xfce Spin and Zenwalk, but there is a good chance your favorite distro provides packages as well.
You can find a more complete list at DistroWatch.com.
You can download the Xfce artwork tarball here. It contains some high-quality logos and banners. Copying of the Xfce logo is subject to the LGPL copyright license.