Besides being available with Linux and FreeBSD kernels and then the horde of GNU packages making up the user-land, Debian 6.0 is available for the usual array of architectures plus PowerPC, SPARC, MIPS, Itanium, and ARM. The Debian GNU/kFreeBSD port is currently available for 32-bit and 64-bit Intel/AMD systems.
Aside from introducing the kFreeBSD flavor, Debian 6.0 also takes the controversial step of removing closed firmware from the kernel.
Some packages found in Debian 6.0 include KDE 4.4.5, GNOME 2.30, X.Org 7.5, OpenOffice.org 3.2.1, Linux 2.6.32 kernel, GCC 4.4.5, and Xen 4.0.1.
There's a very lengthy announcement of Debian 6.0 over at Debian.org. At the same time as releasing 6.0 Squeeze, they also decided to overhaul their web-sites too.
Previously I have done benchmarks of Debian GNU/kFreeBSD along with comparing the performance of Etch, Lenny, and Squeeze but now that 6.0 Squeeze is official, some new tests may be on the way.