First8 and Amis teamed up to organize an introduction session on the day of the release. In this almost three hours long session all major new features of Java 8 were introduced. A lot of questions were answered about Lambda expressions, the new Stream API, the new DateTime API and JavaFX 8. The slides of the session can be found here (First8 part of the session) and here (Amis part of the session).
Read about the launch event on the Amis technology blog.
To start using all the new features of Java 8 you need to download the Java 8 JDK which can be found here.