Proper CSS
It appears that IE7 will fix numerous bugs in CSS support. That did not seem particularly newsworthy — I had seen Zen Garden just like everyone else, but for my purposes IE displayed CSS well enough — until I read about two very interesting uses for CSS that are not supported by IE6. First, using :hover, one can make collapsable menus with no javascript. Yes, no browser detection, no per-button graphics, none of that impossible-to-maintain nonsense. Pure HTML and CSS. Hopefully IE7 will support it (at which point I will start using it on my pages). And second, using background-attachment: fixed, one can implement all sorts of neat effects with no jittering and no javascript.
Alas, the state of CSS support in the first public beta of IE7 does not seem too encouraging.