The most popular types of flash memory cards for use in digital
cameras are: Secure Digital (SD), CompactFlash (CF), Memory
Stick (MS), MultiMediaCard (MMC) xD-Picture Card (xD) and
SmartMedia (SM).

The type of memory card you use is dictated by which digital
camera you buy. These cards are physically different and are
-not- interchangeable.

eBay has become notorious for "fake memory card" sales,
thousands of people have been scammed by sellers who
are selling inferior or lower capacity cards that have been
relabeled and repackaged to look like the real thing. Buyer
beware - I recommend that you purchase your cards only from
reputable online vendors or brick and mortar stores. If you
must buy on eBay then check out this page at Overclockers.
com.au for ways to visually identify some (not all) of the most
popular fake cards. Also see our public discussion forum for more info.