I've just spent a couple of weeks gathering up every version of the source code and the game files that I could find. Jason's GitHub collections are excellent, but they are an edited extract from one source: the so-called "Infocom Drive". They omit some published variations, beta-tests, and so on.
For years, the IF Archive has had another collection of Infocom game files (though not source code): the patches collection. But these were in an annoying encoded format, in order to dodge the legal problems with archiving commercial games.
I figure that those legal problems are well out the barn door now. It's time to have every Infocom game file variation in one place, indexed and easy to download. So here they are:
I've tagged everything with the release number and serial number, where known. Plus tags for whatever other info we've got: "alpha", "beta", "mac", etc.
Research and enjoy!