All 40 TurnKey Linux AMIs now free in all Amazon EC2 regions
turnkeylinux.org
turnkeylinux.org
Add the fact that turnkey actually uses fresh packages for many appliances and uses only the kernel+base system of Ubuntu LTS, it makes perfect sense.
Note that Ubuntu 8.04 is a Long Term Support (LTS) release which will continue to be supported by Canonical with security updates for another 3 years (until April 2013).
All appliances will be rebuilt on top of Lucid (the new LTS) when it is released at the end of the month.