The Squawk Project - Research Java VM, examines better ways to build VMs. Most commercial VMs are coded in low level languages: C, assembly. Goal: write as much of VM as possible in Java, for portability, debugging, maintainability. Inspired by Squeak project. - http://research.sun.com/projects/squawk/
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] - http://orp.sourceforge.net/
Sable Research Group - Publications - Papers and theses on optimization and efficiency of Java virtual machines. - http://www.sable.mcgill.ca/publications/