One of the few remaining points that Firefox scores over IE7 is inline search - I've always found the popup to be much less intuitive (and for that matter useful!) than the way that it worked in Firefox.
Installation is as simple as running the installer and restarting IE, from that point on the new inline search pops up where you would normally have seen the floating window, and it's keyboard driven (so F3 does a "find next" just as you'd expect).
Currently they don't allow you to customize the keystrokes it uses, or keep a history of searches (and there's no 64 bit version) but the development seems to be active and on-going.
My only wish... that I'd found this a couple of years ago! Along with the IE Script Debugger and Developer tools this is one of those essential add-ons that everyone should know about.