Hi!
Straight from the horse's mouth, that is, from the EJB 3.1 Specification:
New in EJB 3.1:
• A simplified Local view that provides Session Bean access without a separate Local Business interface.
• Packaging and deployment of EJB components directly in a .war without an ejb-jar.
• An embeddable API for executing EJB components within a
Java SE environment.
• A Singleton session bean component that provides easy access to shared state, as well as application startup/shutdown callbacks.
• Automatically created EJB Timers.
• Calendar based EJB Timer expressions.
• Asynchronous session bean invocations.
The above are nice improvements which, in my opinion, makes EJBs much more usable.
If you are new to EJBs, then studying EBJ 3.0 and later taking a look at EJB 3.1 using the specification documents or new books available then is a good plan, I think.
Best wishes!