I had been watching some videos from YUI Theater. A lot of interesting stuff is there about client-side and front-end web development.
Must see videos are from Douglas Crockford — "The JavaScript Programming Language" (see all the 4 parts there).
But I really like one from from Joseph Smarr — High-performance JavaScript: Why Everything You've Been Taught Is Wrong.
He gives overview of a real-world Web 2.0 web application (Plaxo) and explains that many things that are in general a good practice (including patterns) are not always good. Just because of the performance.
Joseph says he met a guy who was so proud that he applied all of the patterns (that he knows?). But was there a need of it? Maybe yes, maybe not. But:
Always think about performance, from the beginning to the end.
See the video: