Mac 101: Applications in the Finder toolbar
Last year (pre Mac 101) we told you about the ability to customize your Finder toolbar with folders for quick access, but you can also put applications there to use with drag and drop operations. For instance, in my Finder tool bar I have AppZapper, ImageWell, and Path Finder. This way I can easily uninstall applications, do simple image edits (especially resizing), or reveal the file in Path Finder just by dragging things onto the appropriate icon. This can be a real time saver for any applications you use regularly, particularly by drag and drop.
To customize your Finder toolbar, just right-click on an empty area of the toolbar and choose "Customize Toolbar..." You'll want to have another Finder window open to your Applications folder and then you can just drag and drop application icons from the other Finder window onto the toolbar of the window with the customize sheet open.
Update: As several folks have rightly pointed out you don't need to use the "Customize Toolbar..." command, though I was under the (perhaps mistaken) impression that Apple officially recommended doing it this way.