You can take a look at JavaWorld, they even have a newsletter to which you can subscribe.
But I would like to mention that you will never be able to know all Java libraries and technologies. Some things you might never need and thus will not come in contact with. It does not have to mean that you are not good at what you do! For example, why do you have to know about the Telephony API when you are a Website developer.
Also, even after using Java for many years I still make heavy use of the API docs. This doesn't mean I don't know the technologies - just that certain method signiatures elude me quite frequently. The key point to know where to look for information - what class and method.