The following are some Polyglot-based projects that we know about.
The list is incomplete.

HydroJ, Object-Oriented Pattern Matching for Evolvable Distributed Systems,
    OOPSLA 2003. Keunwoo Lee, Anthony LaMarca, and Craig Chambers, UW.
http://www.cs.washington.edu/research/projects/cecil/www/pubs/hydroj.html

PinPoint, a source code bug injection tool. Emre Kiciman.

XJ, adding XML support to Java (at IBM)

JPred, a language that extends Java with predicate dispatching (Todd Millstein)

Jedd, a BDD-based relational extension of Java (Ondrej Lhotak, McGill)
http://www.sable.mcgill.ca/jedd/

MAO, a Modular Aspect-Oriented language (Curtis Clifton, Iowa State)

abc, the AspectBench Compiler (Oege De Moor, Laurie Hendren, Aske Christiansen et al.)
