The Quero Toolbar is a navigation bar replacement for Internet Explorer that offers a built in ad-blocker. With Quero, you can customize the UI of IE, allowing you to resize, move or shorten your address bar again. Then integrated ad blocker stops unwanted Flash, banner, layer, Google, IntelliTXT, and pop-up ads. Other features let you highlight search terms on your pages, begin finding as you type, search or highlight any word by selecting and right-clicking it, and jump to URLs that aren't highlighted.
The latest version supports Vista's Aero theme (for Vista users) and lets you just use Quero as a button, instead of an entire address bar replacement.
An IE8 version is in progress if you are beta-testing the the new browser.
Otherwise, you can download Quero from the Quero homepage.