Perhaps this has been posted before, but here it is again:
http://www.virtualaltair.com/virtual...vac_boards.asp
It's a fairly comprehensive list of Altair brand boards, and many entries have links to original Altair advertising copy. There are some Altair 680 boards, too.
A wish list:
88-PMC8 (8 KB PROM board using 2708 EPROMs; need a programmer as well)
88-16MCS x3 (16 KB static RAM board; three for a total of 48 KB RAM)
88-2SIO (Dual port serial I/O)
88-VI/RTC (Vectored interrupt/real time clock; may need hacking to work with modern power supply)