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.
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.
Yap4j is the simplest library for parsing CSV files in Java. It deserializes CSV files into a list of POJOs using a set of Java annotations, while allowing you to specify Object-CSV mappings. It automatically converts to and from a wide range of data types, and includes support for types from popular libraries such as Joda Time, and support for custom record delimiters.