I'm loving the work many of my former teammates (I was an IE PM working on DHTML's programmibility from IE5 to IE6) are doing over on IE7.
Keyboard (or mouse) shortcuts I like:
ctrl-t - opens a new tab
ctrl-click on a link (opens in a new tab in the background)
ctrl-e, moves keyboard focus to the search box, type your term, then:
1) enter to navigate the current tab
2) alt-enter to navigate a new tab
See more at the Keyboard Lover's Guide to IE7.
Search Providers
Adding search providers is nice: http://blogs.msdn.com/ie/archive/2005/09/14/466186.aspx
Search on this site
Navigate to a site with a <link /> tag pointing to information about their search, and it shows up in the drop down box next to search...
For instance...go to live.com and see how the drop down changes. (it changes color and adds some choices in the drop down...)
Install IE7 Preview?
If you haven't tried IE7, now may be a good time:
Internet Explorer 7 Beta 2 Preview - released on March 20th.