I figured I'd actually try and log this stuff. So besides the original releases, we have...
1978
Episode IV re-released with "Episode IV: A New Hope" added after "Star Wars."
At some point, the films were released on VHS. I'm not sure if it was the only VHS edition ever released, but the one I grew up on was the "half-face" covers, with the Leonard Maltin interviews at the beginning.
1997 - Special Edition
Changes include...
Episode IV -
- Two deleted scenes, one with CGI Jabba the Hutt and Boba Fett added in;
- Added digital effects in Mos Eisley scene
- Deleted orange blur beneath Luke's landspeeder
- Added effects of pilots inside their X-Wings
Episode V
- Added scenes of snow monster
- Digitally expanded Cloud City
- The Emperor's cry from RotJ is added as Luke falls down the shaft (that was weird. What did they do with the same cry in RotJ?)
Episode VI
- Added new musical number to Jabba's palace
- Deleted black bars around the Rancor
- Digitally added beak to the Sarlaac
- Replaced Ewok's song with a new one, still John-Williams-penned
2003?? - DVD Editions
Changes include
Episode VI
- Hayden Christensen replaces Sebastian Shaw as Anakin's Force-ghost
Due to popular demand, at some point the original editions of the trilogy were released on DVD.
20?? - Blu-Ray
Changes include
Episode VI
- Ewoks blink
Later The Phantom Menace Release
I'm not sure for what edition this was, but Yoda was later replaced with digital Yoda.
The entire saga was later released on Digital HD, I'm not sure if there were any changes there, and the latest (IE the Blu-Ray version, if I'm not mistaken) is what's streaming on Disney+. The original versions of the films have never been released in HD, although I'm sure there's a huge movement for that!
Other Changes - I'm Not Sure When They Occured
Episode V
- "Luke's" scream as he falls is removed, restoring the original version.
Episode VI
- Darth Vader screams "No!" as the Emperor electrocutes Luke
- Anakin's eyebrows are removed.
Can anyone help me out with the dates, or name any other changes.