YAJL (Yet Another JSON Library) is a small event-driven (SAX-style) JSON parser written in ANSI C, and a small validating JSON generator. It's highly portable, data representation independent, fast, generates verbose error messages including context of where the error occurs in the input text, can parse JSON data incrementally off a stream, and is tiny.
The Parsing Expression Grammar Template Library (PEGTL) is a C++0x library for creating parsers according to a Parsing Expression Grammar (PEG). Grammars are embedded as regular C++ code, created with template programming (not template meta programming). These hierarchies naturally correspond to the inductive definition of PEGs. The library extends on the subject of PEGs with new expression types, actions that can be attached to grammar rules, and mechanisms to ensure helpful diagnostics in case of parsing errors. PEGs are superficially similar to Context-Free Grammars (CFGs).
stupid-xml is a ridiculously simple annotation-based XML stream parser for Java. The main goal of this project is to get the strings you care about out of XML and into Java as quickly as possible. You define a simple model class, specify the relative paths for its fields, and it will start generating instances for you from an XML stream. The functionality is limited. It will only parse Strings into your model, but this keeps everything extremely simple. Once you have the Strings in your model, you can perform filtering or more complex conversions.