CD-R - CD-R/RW disc; currenly only a few Sony cameras can write to small CD-R/RW discs.
CF - CompactFlash card - one of the most popular memory cards
CF2 - CompactFlash Type II card; these are thicker than regular cards and only work in cameras with a type II slot. Cameras with a Type II slot also support regular CF cards.
Floppy - Floppy disk; images saved to 1.4MB floppy; these cameras are rare these days.
MMC - MultiMedia card; similar to SD but slower and lower capacity.
MS - Memory Stick; Sony's proprietary memory card format; limited to 256MB capacity (128MB x 2 to be exact).
MSDuo - Memory Stick Duo; Sony's proprietary compact memory card; Regular Duo cards top out at 128MB; Pro cards go up to 4GB. All Duo-supporting cameras can use the Pro cards
MSPro - Memory Stick Pro; High speed, high capacity version of the Memory Stick. Requires a camera that supports these cards.
SD - Secure Digital card; a compact card that is fast becoming an industry standard.
SDHC - Secure Digital High Capacity card; like SD, but faster and with higher potential capacities
SM - SmartMedia card; once very popular, no longer found in new cameras
xD - xD Picture card; this replacement for SmartMedia is very small