JarFish is a useful tool for dealing with Java classpath issues.

It lets you search all the jar files under a specific folder to find a given class.
Example: java -jar jarfish-1.0-rc7.jar find ClassBeingSearchedFor C:\projectFolder\lib

The package name prefixes (such as com.abc.) do not need to be included in the class name that you list in the command, but the class name is case sensitive.

It also lets you search all the jar files under a specific folder to find any classes which exist in more than one jar file.
Example: java -jar jarfish-1.0-rc7.jar dupes C:\projectFolder\lib

A Survey of the JavaScript Programming Language - a very good high-level overview of JavaScript, for programmers who are already familiar with other languages.

I thought I was already fairly knowledgeable about JavaScript, but it has many neat features that I wasn't previously aware of.