I recently swapped my HTC Hero for a Motorola Droid to be able to check out the latest that Android 2.0 has to offer. I purchased mine at full price without contract since I did not need to use the Droid as my primary phone. Upon starting up my Droid I was presented with a screen that wouldn't let me do anything until I activated service with Verizon. After scouring the web for solutions I came across one little trick, which has allowed me to use my Droid without service.
On the activation screen if you do the following you will be able to use your Droid.
Touch the top left corner, then the top right, then the bottom right, then the bottom left - counter clockwise.
Now you should be able to enjoy all that is Android 2.0 on that glorious screen, which makes my iPhone very jealous. You also won't have to do this tap dance again until the next time you fully power off your Droid and power it back on.