Official Java website home page.
The Java API. - Describes all the standard Java packages – this is a very useful link.
The Java Language Specification.
Here are instructions for installing eclipse.
Pointing Eclipse to a particular JVM
For mac users, here is an article on how apple treats java that might be helpful: http://java.about.com/od/gettingstarted/a/Java-7-And-Beyond-And-The-Mac-Os-X.htm