Ubuntu 12.04 will, when its released later this month.

Debian Backports has a 3.2 kernel for Squeeze.

Fedora 16 is on 3.3.0.

Arch, which should be moving to 3.3 soon. Obviously not really a server distro, but still an option if you really want/need bleeding edge.

opensuse tumbleweed (install 12.1 and then follow instructions at http://en.opensuse.org/Portal:Tumbleweed).

not as stable as a standard release though, in my experience (which was a while ago - stability is an important aim for the project, so they may have got better).

The soon-to-be released Ubuntu 12.04.

Gentoo.

Debian testing.