JDocs.com

JDocs.com: "JDocs is a comprehensive online resource for Java API documentation. All the javadocs for a variety of popular packages are loaded into our db-driven system, and users can contribute their own notes to virtually any class, field, method. In short, JDocs provides a knowledge base defined around the major Java api's themselves, so you can find the information you're looking for right where it should be... in the documentation!"