lightJacc is a small but strong grammar parser generator. It adopts a parsing strategy of its own: dynamic concurrent parsing -- which made it much stronger than LR or LL family CCs (YACC, ANTLR, etc), but still keep good performance.
The VISL Constraint Grammar Compiler is a natural language parser generator. It is an implementation of Pasi Tapanainen's CG-2 constraint grammar formalism.
The VISL Phrase Structure Grammar Compiler is an implementation of a parser generator for ambiguous context-free grammars, ambiguous input, and ambiguous output.