Grammatica is a C# and Java parser generator (compiler compiler). It improves upon simlar tools (like yacc and ANTLR) by creating well-commented and readable source code, by having automatic error recovery and detailed error messages, and by support for testing and debugging grammars without generating source code.
MagpieRSS provides an XML-based (expat) RSS parser in PHP.
MagpieRSS is compatible with RSS 0.9 through RSS 1.0. Also parses RSS 1.0's modules, RSS 2.0, and Atom. (with a few exceptions).
LLnextgen is an Extended-LL(1) parser generator. It is a rewrite of the LLgen parser generator by D. Grune and C.J.H. Jacobs which is part of the Amsterdam Compiler Kit (ACK). Like all parser generators, LLnextgen takes the description of the grammar with associated actions as input, and generates a parser routine for use in compilers and other text processing programs.