In general, cards are getting so cheap these days that it really doesn't matter (in my mind) what format it uses. If you like the camera, then just go ahead and get the thing. For the record, media card formats are as follows:
xD is proprietary as mentioned before for Fuji and Olympus only
Memory Stick (MS) is proprietary to Sony
SD is the most widely used and is used by pretty much any other camera company
There are multiple older formats such as MMC, Compact Flash and so on that are not used in new cameras any more.
However, one other major difference can be the speed at which the card records the image. The SDs are a bit faster, and you can purchase faster cards for a bit more. The xD cards are only available in the standard speed. If the aspect of how fast the camera will be ready for the next shot is an issue for you, look into an SD card, otherwise any of the available cameras should be fine.