Antlr
ANTLR is a parser generator tool.
BITPlan has been using ANTLR in projects for a few years now and Wolfgang Fahl has been active in improving ANTLR see e.g. #Motivation
Library with helpers for ANTLR Language development com.bitplan.antlr
To simplify Parser development with ANTLR BITPlan has created a library with some helper code for ANTLR Language Development and published it as Open Source at:
Base Class Language Parser
The abstract Base Class LanguageParser has some help code that makes Language Development and debugging easier.