Flash Design
Adobe Flash is among the richest and most complex platforms available for the web, and is the standard for video (FLV, at least until HTML5 is released, but that's many years off). Flash allows objects to fly around the screen, dissolve into each other, and interact with the user in ways only dreamt of just a few years ago. The challenge web designers face is to use its full potential without making the site too bloated and "flashy."
Flash has another drawback: it's not available on the iPhone, and will probably never be. Apple and Flash have a long-standing rivalry, probably because Flash is so powerful and circumvents Apple's control of the entire experience, and Steve Jobs announced recently that the iPad will continue the trend. It's a battle of major players with no end in sight.
This is why many web gurus recommend building two sites: one with Flash for the richest experience and one without for the widest possible audience. Code can be implemented which determines whether the user has the Flash plugin installed for their browser (most do, although not always for Flash Player 10/ActionScript 3.0, the latest version) and asks the user for their choice.