I remember seeing the original Star Wars on the first day it was released in my city (which, sadly, was a few weeks after it was released in many cities). Being a young geek who could only get SF in books and once a week from Star Trek reruns, I saw it as many times as I could that summer and it was etched firmly on my brain.
Within a year or two there was a re-release. I'm pretty sure this was not the re-release with footage of The Empire Strikes Back and a few friends and I noticed they had, at the time, added echo effects with Luke and Leia in the chasm.
That was my first experience with movies being retconned. As we all know, along the way, Lucas has made a number of changes to the original trilogy, mostly to the original Star Wars (including adding "Episode IV" to the title).
Is there a list of what changes, revisions, and retcons have been done to the Star Wars movies and when they've been done?