Im sure most of you who collect know this, but if you dont, their is a company called eagle one media (
www.eagleonemedia.com) who have been officially putting a ton of these older/newer series to view on dvd- rom
I found out about them as they just released the older Deadworld comic series on a cd-rom
but they do offer 40 years of
spiderman (501 issues)
X-men (485 issues)
fantastic four (550 issues)
and more.
The issues are in adobe pdf format. A great way to collect or find out more about the history without spending a fortune in trying to actually get all of these comics individully.