What are the various interfaces used on memory devices
Various memory devices are in general covered by JEDEC standards.
You may find them on their official website.
DDR1/2/3, CFI (for flash memory) are covered by their standards.

It may be really useful to go through data-sheets of the chip manufacturers to better understand some details. I would go with excellent data-sheets of Samsung (DRAM, flash), Spansion (flash), Freescale (processors that access these memory devices). You may find all of them on the Internet for free.