Can you use any unlocked Motorola Droid phone for Android development? Say one you bought off of eBay?
You can use 'nearly' ( I say nearly just in case there are some exceptions that I'm not aware of) any phones for dev, just turn on "allow usb debugging n the settings.
Regarding the motorola droid, it works fine I have one at work and just plugged it in and launched my app.
for further reference, some phones are not recognized in the default settings of the android sdk (the htc legend for exemple), in those cases it is a simple matter of adding a line in your android sdk files (full procedure findable in 30 sec on google).