The Internet Archive has started a Historical Software Collection. This is part of a larger Internet Archive Software Collection that has a number of collections. What is cool is that they have an in-browser emulator that allows you to play with historical software like Visicalc or Atari’s E.T. in the browser. This is a Javascript version of MESS called JSMESS. They are not just archiving the code, but ensuring that there are ways to try the software too.
I learned about this from David Rosenthal’s blog entry on In-Browser Emulation which is worth reading.