In the new version of Internet Explorer, IE8 beta, managing your add-ons is now a lot easier. The new UI looks a lot more like a Windows File Explorer window or the Control Panel, with a list of Add-On Types on the left and Names & Descriptions on the right. From here, you can easily enable, disable, or remove add-ons using the buttons at the bottom right. Most of the changes will take place immediately, but a few (like disabling a toolbar) will require a browser restart.
The new Add-ons window also has new features like support for Ctrl + Click (or drag), if you want to select multiple add-ons at once. Right-clicking on add-ons gives you context menus and the details about an add-on can be copied to the clipboard and pasted into a document or email.
I learned about these features and a lot more over on the IE blog, where developers can read about what IE8's new add-ons mean for them, too.