Classic IE9 and Classic Explorer aren't as exciting to me, perhaps because I use Google Chrome as my browser and Directory Opus as my file manager. Still, if you do use Internet Explorer 9 or 10, Classic IE9 improves its interface by including the current website's title in the window title bar, showing the current security zone in the status bar, and showing the loading progress in the status bar.
Classic Explorer fixes Windows Explorer annoyances by adding a toolbar with common operations (copy/paste, go to parent folder, etc.), showing the free disk space and the total size of the selected files in the status bar, disabling breadcrumbs on the address bar, and more. Much like Classic Start Menu, it is very customizable, so you don't have to use all of its features (for example, I quite like the breadcrumbs, those clickable elements in the address bar that let you go back up the folder hierarchy, and Classic Explorer let me keep them).
Before you spend any money on a Start Menu replacement for Windows 8, you absolutely must check out Classic Shell. Its lean and customizable menu gets the job done with no fuss, and gives you the exact Start Menu you've always wanted, no matter which version of Windows it comes from.
Note: The Download button on the Product Information page will download the software to your system. This file is donationware; the developer offers it for free, but encourages donations toward its development.