DocJar: Open Source Java Code Search Engine
This site collects more than a thousand Open Source Java APIs. Users can browse Java documents and source code. It also has a free Eclipse Plug-In to allow users to browse the site from thier Eclipse IDE.
Help4j
Repository of code examples from open source projects, tips, links and utility classes organized by Java method and class. Windows and Unix/Linus versions. Integrates with JavaDoc.
Java Gotchas
Tricky parts to the Java computer language - quirks, features and nasty surprises, and how to get around them.
JSP and Servlet Reference Materials
Free PDF of course materials from training courses on JavaServer Pages (JSP) and Java Servlets.
The Java Home of Kaan
The Java Scratchbook and shortcuts : code samples and examples sorted by package names. Java Certification programmer exam questions and answers. JDBC/ODBC connection with MS Access. Terras Game. Topics Deployment Directory Services (Dutch). Quality Pro Netscape Administration Directory Example (Dutch)