A system called the 'Prometia' is available that works using 'phase change' technology for cooling. Have a look at this little thing on overclockers:
http://www.cpudatabase.com/CPUdb/
This little Database shows CPU's registered from different areas with different cooling. Most impressive is the Pentium 4 2.4C/800 bus at 3900MHz.
There is a P4 3GHz/800 bus at 4.GHz however.
These systems are both with Prometia, a review of it can be found
here.