The Ubicom (formerly Scenix) SX52 has a Java VM available. It is not intended for other than very serious applications (the license is $25,000) but it does include source code and can be extended (some) to add Virtual Peripherals for additional hardware support. It executes byte codes from an external memory, so the Java program size can be quite substantial.
http://www.ubicom.com/java_vm.html
Although cost is... stunning?... The idea behind this approach is quite exciting to me... You have a two chip solution that can
Hobbyists should look at XPL0 for a similar but open source solution.
See: