MaxMax is an easy-to-use tool that emulates the Windows Vista sidebar on Windows 7.
Once installed, then, maximised applications will by default no longer cover the entire screen. Instead they'll leave a border on the left-hand side where your gadgets can run on their own.
If you're not keen on the default settings, that's not a problem. The MaxMax system tray icon allows you to reconfigure these, so you can have the sidebar on the right, at the top or bottom of the screen, and then tweak it to be whatever size you need.
And if there are still some applications where it causes problems, then that's also not an issue. By pressing a selected hotkey (left shift by default) you're able to disable the program temporarily, and so fully maximise whatever other apps you might happen to be using.