In my line of work, I'm constantly opening and saving files in myriad folders scattered across my hard drive. It seems like every time I face an Open or Save As dialog box, it means I have to spend considerable time navigating between folders.
That's why I'm a big fan of Windows 7's Recent Places feature, which appears under the Favorites heading when you open an Explorer window. Take a look:
Recent Places is not quite the same thing as the Recent Documents option you may have seen in the Windows Start menu. When you click the former, it shows you a list of the folders you've accessed recently. Click into the one you want, choose the file you need, and presto, you're done. No need to waste time navigating various drives and subfolders.
If you don't see the Recent Places option (or any kind of lefthand pane in your Explorer window), you'll need to make it visible. You can do so by clicking Organize, Layout, Navigation pane.