My post in How would you use a Raspberry Pi:
Sticking it (RasPi) inside a case that allows you to easily remove and install the SD card, through a slot in the case, would work well. Placing a connector on that case that will allow you to plug it into different interfaces. Plug it into a mini keyboard, battery and small LCD and it is portable. Plug it into a LAN/USB/power (model B) and you are ready to use it as a personal computing device on your desktop. Of course you will have to plug in a monitor when you need it. With only a few 4GB SD cards you could have half a dozen different uses for 1 or 2 (or 3) RasPi's. You can also hardwire from the SD card slot to the multi connector. Every time you plug into a different interface you would also be plugging into a different SD card. You just leave the appropriate SD card in the external connector.
In the Physical design thread I proposed placing a connector on one end of the board or case. In this connector would be 8 pins for Ethernet (6 needed for 10/100), 8 for USB (4 pins each port), At least 4 pins for power (2 power 2 ground), 3 pins for sound plus 2 pins for Composite video and 5 for the SD Card. Thats 30 pins in all. I would not try to convert the HDMI as I feel there is too much risk of damaging the board there. This is actually interesting in that with the SD card on the interface side of the connector you would only have to pull the "Computing Core", The RasPi, and replace it with another RasPi When the next versions come off the line you would add the connector to them. You would then have to unplug the old RasPi. replace it with the new version, then plug it back in. The software will be loaded from the SD card that is still in the connector. Granted there may be newer software that is needed for the newer version, but something like a server which is not really concerned with video probably will not even care. This could be done to a board by bolting a plate for the connector to it. Or attaching the connector to a case. You could pigtail all of the connections from the board to the connector if you did not want to go through desoldering and resoldering all of the connections.