Zabbix/J is a framework for integrating Zabbix monitoring into Java applications. Zabbix is an "enterprise-class Open Source distributed monitoring solution" which provides telemetry and triggers across entire infrastructures. Zabbix/J makes it simple to expose metrics from your Java applications, giving them visibility as first class citizens in a Zabbix configuration.
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.
CmdOption is a simple annotation-driven command line parser toolkit for Java 5 applications. Everything you need is (at least one) simple configuration object. Each field and method annotated with an CmdOption annotation will be processed. Based on this config, CmdOption is able to parse any command line, guaranteeing the declared specification. The result is directly stored in the given config object. When errors occur, CmdOption gives a meaningful error message. Generated output and validation/error message can be localized.
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.
mechanize is a stateful HTTP/HTML client library written in Java to be available on the JVM. It utilizes Apache HttpClient for HTTP handling and JSoup for HTML parsing. Because mechanize is stateful, it will by default support cookies and hidden form parameters (like Rails CSRF protection). This enables client code to follow links and behave like a RESTful hypermedia client more easily.