I'd like to introduce a new tool I've been working at during the past weeks: disper. It is a tool to configure displays from the command-line. Although it implements only a small subset of the functionality of nvidia-settings, it is just enough to make attaching a beamer and get going right away quite easy. Disper tries to be sensible about choosing resolutions when cloning or extending displays, but you can override it. Please look at the program's --help option for details.
As the project has just entered an alpha-state (take note, it might do things you don't expect), please test and report any bugs you find in this thread or via email. I hope this tool will make your life easier, especially for those who don't have a working Fn-F7 (or similar) on their laptop.
Ubuntu packages: http://launchpad.net/~wvengen/+archive
Development code: http://code.launchpad.net/disper/trunk