I’m a big fan of dzone which is more than a great digg-like for the developers community. It’s another great tool to be used as part of your technical-watch toolbox whether you’re a developer or a tester.
They also offer a number of very useful cheat sheets on various technical subjects. It’s well-written, filled with useful tips and source code examples and best of all it’s free ! I’ve tried to compile those which I think could be useful for a software testers operating in an agile environment.
You can find all dzone cheat sheet here