One "goodie" that we find most useful is a small inverter for powering our laptop computer— either while we are boondocking or for the co-pilot to catch up on trip journals while we roll down the road to our next stopping spot.
We especially like the very small and slim Xantrex Pocket Inverter 100—just the right size (100 watts) for powering our laptop computer without needing to run the generator or be plugged into shore power. One feature we like is the dual power plug—that fits both a standard automotive cigarette lighter socket, as well as an airplane plug-in (for those few commercial airplanes that provide a 12-volt power outlet at each seat).
This handy little inverter also has a USB socket on it, so that your iPod, MP3 player, GPS, (or any other item that can be charged through a USB port) can be charged without having your computer powered up.
We usually just leave the inverter plugged into a power outlet on the passenger side of the instrument cluster housing—making it within easy reach of the co-pilot. However, when we are boondocking, the inverter gets moved back to the bedroom (where the vanity serves as the computer center), complete with a printer that sees a lot of use as a copier and also has slots for downloading our digital camera memory cards.