JCPP is a complete, compliant, standalone, pure Java implementation of the C preprocessor. It is intended to be of use to people writing C-style compilers in Java using tools like sablecc, antlr, JLex, CUP, and so forth. It has been used to successfully preprocess much of the source code of the GNU C library.
jdiagnostics is a library of routines for inspecting the state of a JVM and building a support bundle. It makes it easy to diagnose issues with classpaths, resources, serviceloaders, versioning, XML parsers, and so forth. It has no dependencies, and is an essential library to build into any infrastructure application.
jmemcached is a fast network available cache daemon. It is protocol-compatible with memcached, but written in Java and suitable for applications with portability concerns, where Java is the preferred solution, or for using the memcached protocol in embedded applications with alternate storage engines. Existing clients for memcache work unmodified. It can run as a standalone daemon or be embedded inside an existing Java application.
jminix is a simple embeddable restful JMX console. It is useful for when you don't want to use an external full-blown JMX console, but just want to have a simple JMX entry point into your new or existing apps. Embedding JMiniX in a Web app is done simply by declaring a servlet. Deployed as a servlet, it benefits from your Web application configuration such as filters or security constraints.
jmxsh is a fully scriptable command-line JMX client based on Tcl. It is simply a Tcl interpreter powered by Java/Tcl (with command-line history and editing provided by JLine) that has special command-line options for connecting to JMX servers and special Tcl commands for interacting with JMX servers. jmxsh is capable of simultaneously connecting to multiple JMX servers. There's also a "browse mode" for exploring the remote JMX namespace without knowing beforehand the names of MBeans or their properties. jmxsh and all its dependencies are distributed in a self-contained executable jar file for ease of use.
jmxtrans is effectively the missing connector between JMX and whatever logging or graphing package that you can dream up. jmxtrans is very powerful tool that reads JSON configuration files specifying servers/ports and JMX domains/attributes and then outputs the data in whatever format you want via special "Writer" objects that you can code up yourself. It does this with a very efficient engine design that will scale to querying literally thousands of machines. The core engine is pretty solid and writers are included for cacti/rrdtool, graphite, and stdout.