WizMouse is a tiny free/donationware utility that has a single, simple, function--if you hover your mouse over an inactive window, and use the mouse scroll wheel, it will scroll that window while keeping it inactive. This can be a boon for anyone copying text manually from an inactive window to an active one, or who needs to see data in one window (perhaps one partially obscured) while reading or working in another. It even scrolls applications that don't offer mousewheel support by converting the wheel to clicks on the scroll bars. In other words, if you spin the wheel down, WizMouse will virtually click the "down arrow" for you.
WizMouse has a very simple interface. Most of the time, it sits in your system tray as an icon; if you click it, you get a small dialog with a handful of basic options. I found the default settings to be perfect.
If this sounds at all useful to you, enjoy.
Note: This program is donationware. It is free to try, but the author accepts and encourages donations towards further development.