SD Card slot
The SD Card slot (Secure Digital) is found on select ThinkPads and Docking stations.
In addition to SD Cards, SD Card slots can also accept the older MMC (MultiMedia Card).
PCI based SD Card slot
This implementation is called "SD Card with IO support", and supports in addition to regular SD memory cards also special SDIO cards (e.g. Bluetooth, WiFi, etc).
Linux support
lspci reports it as a Ricoh device with PCI ID 1180:0822 (X Series), or 1180:0841 (Z Series).
The sdhci project has developed a driver that supports these and other SD controller chips. The driver has been reported to work on a ThinkPad X40 and X41 .
Models featuring this Technology
USB based SD Card slot
This implementation only supports SD Memory cards.
Linux support
Should be supported by the Linux USB Storage drivers (usb-storage).