The propeller can be connected to lots of different things.
NOTE: Links on this page have to be updated. Google searching with the old url generally leads to the updated link.
Which SD-MMC Card ? compares various flash memory card interfaces, DRAM (!), and FRAM.
"SD bootloader -- a very simple EEPROM-resident program that would allow you to pick an image file from an SD card, transfer it to RAM, and boot it. That's it -- no frills, no drivers, just a bootloader."
SPI to and from other devices ... such as the MCP3208 and ADS1271 ADCs... how?
"Fastest Serial Speed?" suggests that it may be possible to "send" up to about 8MBaud. The fastest actual implementation: "Viewport v1.1 transfers data between pc host and propeller at 2Mbps using a single cog... full duplex."
PropNIC - Interface to a ENC28J60 - connect to a local LAN or run a webserver from a Propeller!
MCP2515 - Interface to CAN Bus controller from a Propeller (schematic with object at exchange) - See PropCAN web for pictures (Demo Board CAN I/F, PropCAN) Follow the development of PropCAN at turning on propCAN an engineering notebook Blog.
==SPI combinations
hook the 3 wires up to: +5V and ground (a common ground with the propeller), and a 1 kOhm resistor from the propeller output to the servo input (as discussed above)