LLVM
- A compiler infrastructure designed for compile-time, link-time, runtime, and "idle-time" optimization of programs from arbitrary programming languages. LLVM is written in C++. It currently supports compilation of C and C++ programs, using front-
- http://llvm.org/

Cetus
- An infrastructure for writing source-to-source compilers for C, C++, or similar languages.
- http://cobweb.ecn.purdue.edu/ParaMount/Cetus/

Eli: An Integrated Toolset for Compiler Construction
- Eli is a domain-specific programming environment designed to generate compilers for programming languages from specifications. Eli contains a vastlibrary with precoined solutions and reusable components and is Open Source.
- http://eli-project.sourceforge.net/

Gentle
- A compiler construction system that supports language recognition, definition of abstract syntax trees, construction of tree walkers based on pattern matching, smart traversal, simple unparsing for source-to-source translation, and optimal code selection
- http://gentle.compilertools.net/

PFX
- A tool to create compilers, assemblers, linkers for a range of targets. Special emphasis will be on embedded systems. In development.
- http://pennware.com/language/

Relational Meta-Language (RML)
- Generation of efficient compilers and interpreters from Natural Semantics Specifications. Semantics for real programming languages like Java, Pascal, Modelica were developed.
- http://www.ida.liu.se/~pelab/rml

Free Compiler Construction Tools
- List of lexers, parser generators, code optimizers (optimizer generators), and other compiler construction kits.
- http://www.thefreecountry.com/programming/compilerconstruction.shtml

Mozart
- A set of APIs and a file format that allow various development tools such as compilers, editors, class browsers and others to exchange data and cooperate. Currently, Mozart parses and "renders" only Java, although internally it is language neu
- http://mozart-dev.sourceforge.net/

CoSy
- A flexible compiler development system for languages like C, DSP-C and Java, enabling architecture and compiler developers to generate and reconfigure efficient and robust compilers quickly for their existing and future cores.
- http://www.ace.nl/

Catalog of Compiler Construction Tools
- The resource overview includes compiler construction kits, lexer and parser generators, attribute grammar systems, transformation tools, front- and back-end generators, program analysis and optimization, environment generators, infrastructure/components/t
- http://catalog.compilertools.net/

SUIF
- Extensible compiler system that supports parallelization, object-oriented programming languages, scalar optimizations and machine-specific optimizations.
- http://suif.stanford.edu/

Zephyr
- Its philosophy: build compilers from parts, which might include front ends, back ends, optimizers, and the glue that holds all these pieces together. You might even generate parts automatically from compact specifications.
- http://www.cs.virginia.edu/zephyr/