Do you mean you want to install it on any device from your system, without the need to run Eclipse?
The command would be something like "adb install bin/MyCalculator.apk". Once you do that, your app is installed just like any other.
Do you mean you want anybody to install your app on their device? Your best bet is to just put it on the Android Market. Don't forget to generate a real signing key (don't use the Eclipse debug key) and sign your app properly before uploading it to the market.
If you don't want to use the market, then you can put the apk file on any web page, and have people download it with their browser. Then they go to their device settings and enable "Unknown sources". After that, they can run their browser, go to "Menu > Download" and select the apk they just downloaded.
Or, you can send the apk file to someone directly, and have them attach their device to their computer, enable USB, and copy the apk to their /sdcard directory somewhere. Then they launch a file browser (they'll have to install that first) and navigate to the apk file. I think that will allow them to install the apk on their device.
I think that should cover it.