An image file of the Android 2.1 build for Motorola Droid was leaked last week on Sholes.info complete with instructions on how to install. The port wasn't very accurate, so until a proper ROM is released, we suggest you to wait with the "upgrade".
Click to the source link for creenshots. Meanwhile check out the video of the Nexus One's boot animation running on Droid:
[Continue reading Android 2.1 ported to Droid]