Sometimes you will attempt to deploy your application to a device, but the device you want to deploy to isn't shown in the Select Device dialog. This can happen when the Android Debug Bridge decides to go on vacation.
To diagnose this issue, find the adb program, then run:
adb devices
If your device isn't present, then you need to restart the Android Debug Bridge server so that your device can be found:
adb kill-server
adb start-server
HTC Sync software may prevent `adb start-server` from working properly. If the `adb start-server` command doesn't print out which port it's starting on, please exit the HTC Sync software and try restarting the adb server.