Windows only: Free, open-source application MouseImp Pro adds drag-scrolling to your mouse in most popular applications, including Firefox, Microsoft Office apps, and Windows Explorer. That means you can scroll any supported document by clicking and dragging inside the window (like you often can with PDFs), by pressing and holding the right-click button (by default) and then dragging. The application has other features aside from Direct Scroll, but frankly, it's a little confusing. An AutoShrink feature, when enabled, is supposed to collapse windows to just the titlebar when they're not active to keep your desktop decluttered, but I couldn't get it working. Either way, the simple addition of right-click dragging and scrolling is a nice feature if you like it, and the app takes up a paltry 1.5MB of RAM. MouseImp is free, Windows only.