Wikipedia – SRAM (http://en.wikipedia.org/wiki/Static_random_access_memory), DRAM (http://en.wikipedia.org/wiki/Dynamic_Random_Access_Memory), SDRAM (http://en.wikipedia.org/wiki/SDR_SDRAM), ROM (http://en.wikipedia.org/wiki/Read-only_memory), Flash (http://en.wikipedia.org/wiki/Flash_memory)

 

Books

Digital Integrated Electronics, by Taub & Schilling, Chapter 12 
Digital Design, by Morris Mano (http://cwx.prenhall.com/bookbind/pubbooks/mano2/), Chapter 7 
Microelectronic Circuits, by Sedra Smith (http://www.us.oup.com/us/companion.websites/0195142519/about/contents/?view=usa), Chapter 11, Sec 11.1-11.6