Windows only: Application launcher CSMenu makes up for the lack of the classic start menu in Windows 7 by creating a menu that looks and works just like the ancient Windows 2000 menu did.
Once installed, the application adds an icon to the system tray—but you'll have to pin the CSMenuLauncher.exe file to your Windows 7 taskbar to actually display the menu. You can use previously mentioned Start Killer to hide the regular start button, or you could use them side-by-side instead. If you simply can't get used to the new, powerful start menu, this might be a worth a look.
CSMenu is a free download for Windows 7 only. For more, check out how Taskbar Overlord tweaks the Windows 7 taskbar, middle-click closes applications, or a quick navigation tip shows you the day for any given date.