I found some things about not US Editions of "Caligula"
The UK 4 Disc Imperial Edition is statet to contain something more than the US 3 Disc Edition, according to the german "Online Film Datenbank" But nothing special is said what exactly more. (Maybe I get my hands on it and could compare it with the US imperial Edition)
The Japanese 4 Disc Edition of Caligula is statet to have some more deleted cenes on the 4. Disc, but the Picture is blurred in the hardcore scenes during movie (both versions) and extras!
The scenes on the japanese disc are statet to POSSIBLY be frome the lost cannes cut. But that is just a rumor on ofdb.de.
EDIT:
According to the UK reviews on tzhe 4 Disc UK Box of Caligula, the 4th Disc contains the Original UK Theatrical Version of the Movie. The Movie was cut down to approx. 110 Minutes. So this box seems not to be really better than the US Box. (Except if someone whants to preserver the cut down cinema edition...)
The japanese 4 Disc edition is avaible at yesasia, but.. its about $100 !!! So its to expensive just for a look at the additional Bonus Disc. (Not to say, the blurred scenes...)
ADDITION:
The even as tasteless Movie "Salo - or the 120 days of sodom" is Released in UK on BluRay and relreleased on DVD, full uncut (even the Criterion DVDs were cut), in english, and in italian with english subtitles.
Here are the Informations on the Extras:
Disc 1:
* Complete and uncut, re-mastered from original Italian restoration negatives
* Original Italian language version (with optional English subtitles)
* Original English language version (with optional subtitles for the hearing-impaired)
* Original Italian trailer (with optional English subtitles)
* Coil - Ostia (the Death of Pasolini) The original 1986 track from Coil's celebrated
second album, Horse Rotorvator, with a newly created video accompaniment, shot
especially for this release by Peter Christopherson
-Original italian Trailer
Disc 2:
-Open your eyes! (2008,21min): Pasolini and his actors at work and in interview on set of Salo.
-Walking with Pasolini (2008,21min): Roberto Purvis' new documentary exploring the meaning and impact of Pasolini's film,.
-Whoever Says the Truth Shall Die (1981,58min): the classic documentary on the life and death of Pasolini
-Fade to Black (2001,24min): a documentary discussing the ongoing relevance and power of Pasolini's masterpiece
-Ostia (1987,26min): a short film about Pasolini's last days, presented with optional commentary by director Julian Cole
-48-page illustrated booklet containing a new introduction to Salo by Sam Rohdie;Gideon Bachmann's on-set diaries; reviews and correspondence charting the film's troubled history; sills and on-set photography
The BluRay Edition containing the second DVD, so the content is the same.
(Content listing from ofdb.de)