Vesalia Computer - MMC Replay
http://www.vesalia.de/e_mmcreplay.htm
"The ultimate cartridge for your trusty Commodore 64! MMC REPLAY, as the name already tells, unites the features of the Retro Replay freezer cartridge with those of the MMC64 cardreader. But MMC REPLAY is much more than those two merged together, there are plenty of new features to be found"
ATARI SDrive
http://raster.infos.cz/atari/hw/sdrive/sdriveen.htm
"The SDrive is a device that connects to Atari XL/XE's serial (SIO) port and simulates an Atari floppy disk drive with full read/write access to programs and data stored on a SecureDigital flash card (SD)."