Decompiler from Java bytecode to Java, used in IntelliJ IDEA
A reverse engineering suite (decompiler, editor, debugger and more)
Manifold is a Java compiler plugin, features include Metaprogramming
Learn Java the easy way!
Lightweight IDE for Java
JPHP - an implementation of PHP on Java VM
Best IDE for Beginners
HATE's an ASN.1 Text Editor.
Problemless Grammar and Parser in Java
Pure Trait-based Programming on the Java Platform
a DSL for type systems, reduction rules, interpreters for Xtext langs