Apache Jakarta Regexp is a 100% pure Java regular expression package. Expression syntax supports all of Perl5 syntax, with the exception of back reference substitution markers (several people have mentioned this lack, so please feel free to contribute a solution). It also supports a very limited subset of POSIX features. Performance and features are somewhat inferior to ORO, and the new JDK 1.4 (java.util.regex) package, but the package is especially small and features the ability to precompile expressions (without using object serialization) into byte arrays, thus avoiding the need to load the expression compiler.
arc is an ASN.1 compiler written by FORGE Research for use in internal projects. It is being released under a BSD-like licence. arc creates Java source code that uses the basic ASN.1 classes that were created for use with other FORGE projects. These basic ASN.1 classes are included in the arc distribution.
Avalon is Apache's Java Server Framework project. It is separated into six subprojects: Framework, Excalibur, LogKit, Cornerstone, Phoenix, and Apps. Its purpose is to simplify server side programming for Java-based projects. It formalizes several best practices and patterns for server side programming. Framework describes the interfaces and contracts for the component-based architecture. Excalibur provides a number of useful components and utilities. LogKit is a logging implementation. Cornerstone is a group of reusable server components and services. Phoenix is an enterprise container implementation that uses all of the other subprojects to automatically deploy and manage one or more componentized servers. Apps is a home for several Phoenix-compatible server applications and reusable components (like FtpServer).
Babelj is a language server for Java. It allows programs written in practically any language to fully interact with Java. Client libraries currently exist for PHP3 and Java. Babelj can be used as an out of the box bridge between PHP and Java and adding support for new languages is a snap as well.
Batik is a Java-based toolkit for applications that want to use images in the Scalable Vector Graphics (SVG) format for various purposes, such as viewing, generation, or manipulation. It gives developers a set of core modules (parsers, generators, DOM implementation) which can be used together or individually, and be highly extensible. It comes with a full-fledged SVG viewer.