If you want a smart, free add-on for Internet Explorer, download IE7Pro. The free tool has tons of ways to make IE easier to use, with everything available from one button in the Status bar. IE7Pro stomps on banner and Flash ads, effectively removing most from the sites I visited, but has a tougher time removing pop-up ads; in my tests, most pop-ups snuck through like water through a sieve.
But IE7Pro isn't just about ad blocking. The tool has help you don't get in straight-laced IE, such as Super Drag Drop, a way to drag a link to any spot on the page to open a new tab; and Mouse Gestures, a cool feature that lets you scroll, open, close, and navigate through open tabs. There's also a built-in spell checker and a handy recovery feature just in case IE takes a nose dive and crashes.