The current stable Poky release series is 5.0.1 'Bernard' (released on 25/05/2011). Please see the Yocto Project website for the release notes and more information.
The Yocto release and prebuilt filesystem images for various devices can be downloaded from http://yoctoproject.org/downloads/yocto-1.0.
The Bernard metadata can be downloaded from: http://autobuilder.yoctoproject.org/downloads/poky/poky-bernard-5.0.1.tar.bz2.
Previous releases are available from http://autobuilder.yoctoproject.org/downloads/poky/.
Don't have a supported device? Then check out the Quick Start section in the Poky Handbook to find out how to use QEMU to emulate a device.
Poky is maintained in git at http://git.yoctoproject.org/ which has a browseable web interface.
To check out current development code using git:
git clone git://git.yoctoproject.org/poky.git
Poky currently supports the following reference platforms and derivatives;
Wider platform support is under constant development and new platforms are added easily.