I'm a huge fan of most things O'Reilly. The Safari Online Books offering has become an absolutely indispensable source of reference and learning for me. A new version (5.0) of the service was launched last week and includes a whole load of new features, including Ajax based paging and the availability of a number of graphically rich titles online. I've been looking at the Head First Design Patterns book online and been really pleased at how the visual experience of the book has been translated to my web browser. This is an excellent upgrade to a model service: more usable, faster. All involved should be congratulated.

You might be interested to see what Tim O'Reilly himself says about the redesign here.