"Blast from the Past" is also the name of a collection of games for the Commodore C64.
This collection has around 1900 games enlisted. So if you search for rare C64-games, there is a huge possibility that you may find them there.
One problem remains with this collection : As far as i know, most of the games there are cracked and maybe illegal. But on the other hand most of the game distributors dont care of their old games any more, because they can make no more money with them. In spite of this, the Copyright remains intact though. Maybe a topic which should be discussed with the right people sometimes...
See also Abandonware.