You can bypass the SIM card requirement by playing with the boot options:
- Load Boot menu by holding the Volume Down button while starting the phone.
- Press the Volume Down button until the option "Boot Android (NO BP)" appears at the top of the screen.
- Press the Volume Up button to select this option.
- On load, the phone will bypass the No SIM card screen
Next, you can either register for a MotoBlur account or skip it by entering the following keys into the virtual keyboard (press and hold the Menu key to bring up the keyboard):
Luckily, this process only needs to be performed once. It looks like the phone remembers this boot option for next time :) Thanks to XDA for the MotoBlur bypass steps!