After not being updated for a few mainline kernel release cycles, the real-time (RT) Linux kernel has been updated against the Linux 3.0 kernel release
Thomas Gleixner announced the Linux 3.0-rt1 kernel on the kernel mailing list
yesterday, which integrates the RT patch-set atop the vanilla kernel.
For a verbose update on the state of the real-time Linux kernel, see this earlier email
for a good overview. There's also more information on the real-time kernel via the Kernel.org Wiki