Java SE 8 for the Really Impatient by Cay S. Horstmann. I'd recommend it as an introduction to Java 8 features. I've also read Cay's Scala for the Impatient, and used his Core Java books for reference. No doubt there will be other Java 8 books arriving soon. Pragmatic Programmers has Functional Programming in Java: Harnessing the Power of Java 8 Lambda Expressions in beta. And Manning has Java 8 Lambdas in Action in Early Access. But unless I'm in a rush to learn about something, I don't usually go for beta or early access versions because I'd rather wait and read the final product.
Java 8 has seemed so far in the future that I haven't been thinking about it much. But I see it's supposed to be released in March, which isn't really that far off.
If I was starting a JVM project from scratch, I'd probably lean towards Scala. But for maintaining and improving the jSuneido Java code, I'm looking forward to Java 8, especially lambdas.
The current release version of Eclipse doesn't support Java 8, but there are early access releases available. Presumably support will be included in the next version of Eclipse. Intellij also has early support for Java 8.
Netbeans may be the best bet right now. Version 7.4 has Java 8 support, and the beta for Netbeans 8 is available.