A tool for building parsers, language translators and compilers.
The home page can be found at http://www.antlr.org/.
This list catalogues freely available software for language tools, which includes the following: compilers, compiler generators, interpreters, translators, important libraries, assemblers, etc. -- things whose user interface is a language. Natural language processing tools may also be included.
The home page can be found at http://www.idiom.com/free-compilers.