db4o is an object database for Java and all .NET environments. Its features include ACID transactions, automatic class schema recognition, query-by-example, a S.O.D.A. object querying API, native queries, LINQ support on .NET, callback methods, memory files, cascade-on-delete, multi-threaded access, and Java Webstart and servlet support.
XMLToaster is a tool for extracting and loading XML from databases. It provides a modified version of SQL which has XML mapping extenstions. It can be compared to the "for xml" command in MS SQL Server 2008, but it runs on all common databases and scales to handle very large XML mappings without too much complexity. It is used as a Java library to write XML interfaces, but can also be run as a command line tool.
JTelIRC is an advanced IRC framework for Java. It is mainly intended for writing automated clients ("bots"), but may be used for normal clients as well. It provides an intuitive and well documented Java interface to IRC and makes it extremely easy to write advanced clients quickly.