Book: DHTML Utopia: Modern Web Design Using JavaScript & DOM
It's a great refresh of everything you assume as right regarding websites construction. This is really a great start for Web 2.0 applications, Ajax techniques are also covered by the author, and one methodolgy I really like to develop now is unobtrusive Javascript, which let your users have a better experience with a web application.
If anybody from Sitepoint read me, yes I am ok for a review :-)