If the Mac's support for multiple monitors weren't one of my favorite bragging points, I'd have stopped these notes long ago. However, useful information continues to trickle in, much of it on TidBITS Talk, and it's of sufficient interest to pass on here as well.
First, Tarik Sivonen <email@example.com> comments that an article by Chris O'Malley in PC Computing's May 1998 issue reviews 17-inch and 19-inch monitors, and more importantly, includes the results of usability testing and return-on-investment analysis. The conclusion? In comparison with a 15-inch monitor, a 19-inch monitor can pay for itself within two months. Overall productivity gains in spreadsheet tasks, word processing, and Web browsing increased between about 12 percent and 27 percent for users of 19-inch monitors (again, as compared to those using 15-inch monitors). 17-inch monitors were almost as good for word processing and Web browsing, though not as good for spreadsheet work.
Second, readers submitted additional ways of recovering windows and dialog boxes you can't see after disconnecting a second monitor.
If your Mac supports duplicate monitors (video mirroring), you may be able to recover windows by dragging one onto the other in the Monitors & Sound control panel. Not all desktop Macs have this feature.
Install the $10 shareware control panel DragAnyWindow (a 111K download) from the prolific Alessandro Levi Montalcini. DragAnyWindow enables you to move any window, including dialogs, alerts, game windows, and windows that have disappeared. DragAnyWindow would also be useful for older Macs with 9-inch screens when dealing with overly large dialogs.
Install the $10 shareware program Virtual. When you quit Virtual, it moves all open windows onto the main screen. Virtual is a 329K download.
Use Ross Brown's freeware Virtual Desktop 1.9.2, which, upon launch, adjusts its scroll bars so you can scroll to any existing window or desktop icon. Virtual Desktop is a 217K download
Finally, if you've removed only the monitor, also try removing the video card, since sometimes the Mac will see a monitor if the card is still installed.