In Mail.app, you can open Window → Activity (Command-0) to show all pending networking activities. Cyberduck 3 now includes the same functionality. It gives you a better idea how much longer the progress bar will still be spinning and allows you to stop pending background tasks. Prevously, this was only possible for the currently running task using the Stop toolbar button in the browser window.
Check this out in the the latest nightly build. Mac OS X 10.4 or later required.