Best practices for 2011 Mac mini connected to monitor + HDTV? I'm dual-purposing a new Mac mini (2011) as a desktop machine and media center. I will be using a DisplayPort to DVI adapter to use with the desktop monitor, and a long HDMI cable to go directly to an HDTV at the other end of the room.

What can I expect from this configuration, when the usage pattern is going to be limited to one display at a time? Meaning, at any one time it will either be used as an HDTV source with the HDMI display or a desktop machine with the DisplayPort display. Obviously I'd like to avoid unplugging/replugging cables all the time to disable the displays, and I would probably not like to mirror 1080p to a 1600x900 desktop display.

Changing the audio output from HDMI to internal I can handle with an option-click to the sound menu extra, but there's no such functionality to switch from one connected display to the other that I know of.

Is there anything that I'm missing? Any software that might accomplish this for me?

Anything completely different that might work better?
Your "best practices" will depend a lot on your usage and expected behaviour. It sounds like your preferred option would be to keep both plugged in, but have an option to disable one display at a time. Unfortunately I've not found a way to do this, but there are a few tips and tricks you can use to make things more manageable.

The first is Gather Windows. It's an option in the display preferences that will move all open windows to whichever display you click it on (you get one window on each display). Useful for switching between displays.

If you use VLC, you can set a default screen to use for fullscreen video, under Video > Fullscreen Video Device and choose a screen. Then no matter what display the video opens on, when you full screen it, it will jump to the screen of your choice (presumably you'd set it to your HDTV).

Finally, you may find Moom useful. It's a great $5 app that gives you a bunch of window management options. You can get a demo to check it out. You can set hot keys for actions or use a nice pop-over that appears from the Zoom Titlebar button. Very configurable and useful, I suspect it would be handy in your case.