I've released into public use the Java Reference Card I produced for
use by my undergraduate students. It is a two-side card covering the
language and concurrency & collection essentials. Not surprisingly, it
is rather densely packed.
This is intended as an aide-memoire and a supplement to the on-line
comprehensive APIs and other documentation, and texts such as Java in
a Nutshell 5th edition (which I use as the text for my course).

I have plans for further related developments, and for ongoing
improvements to the reference card. The card itself, as well as
details on how to provide feedback, are available at:
http://www.dcs.gla.ac.uk/~pd/JavaRefCard/

The card can be freely copied for personal, professional and non-
profit educational use. Please do *not* re-publish the card, either
online or in books etc.

I would be particularly interested in feedback as to whether or not
this card has any value for other educators, or for developers. There
is a dedicated email address for direct private feedback
(JavaRefCard@dcs.gla.ac.uk) and a Google group for public discussion
(email: java-reference-card-discussion-group@googlegroups.com).

I hope this proves to be useful,

--Peter