The following post is a comprehensive summary of the developer-facing changes coming in Java 8. As of March 18, 2014, Java 8 is now generally available.
I used preview builds of IntelliJ for my IDE. It had the best support for the Java 8 language features at the time I went looking. You can find those builds here:IntelliJIDEA EAP.

Interface improvements

Interfaces can now define static methods. For instance, a naturalOrder method was added to java.util.Comparator:
public static super