I've not done much Java for a while, but my most useful resources have been The Java Programming Language and The Java Developer's Almanac (especially the code samples, which I believe are available somewhere on java.sun.com).
Effective Java is also a great read for becoming a "better" Java programmer, but may or may not be useful to you right off the bat.
Effective Java is also a great read for becoming a "better" Java programmer, but may or may not be useful to you right off the bat.