Jikes RVM
A IBM research virtual machine for VM researchers to more easily experiment with new technologies. Not a full virtual machine. [Open Source, CPL]
Open Runtime Platform
Research framework implementing advanced JIT and GC interfaces. These interfaces allow the JIT, GC and remaining runtime system to be developed in complete isolation and at independent rates. [Open Source, Intel License]
Sable Research Group - Publications
Papers and theses on optimization and efficiency of Java virtual machines.