I was searching for some Java best practice information on Serializable and came across http://www.javapractices.com/. It's a collection of those rules of thumb that you pick up over the years. I find this very useful as it confirms a number of things that i've thought, and adds to it. Java carries a bit of old baggage around with it so that it's backward compatible and sometimes it is hard to see which is the best method to use. The downside is that when I do my 'wise old developer' act with Doug maybe he'll see through me!
My other favourite is The Java Almanac. I've used the examples many times.