The Star Trek movies have been very interesting in terms of recuts and scenes that still remain unreleased by Paramount. Keep in mind, these just pertain to the films. I will undoubtedly make another post containing unreleased items pertaining to the series.
Star Trek The Motion Picutre -
Contains many different effects shots and tons of deleted scenes. No leak as of yet.
Many scenes from the 1983 television. Mentioned once from OT.com user FanFiltiration.
Star Trek The Wrath of Khan -
Black and white preview cut, many, MANY, alternate or deleted scenes. Abruptly cuts off right when Spock leaves for engine room. Mentioned many a time by TrekBBS.com user Grant.
Title card lacks the II in the title. 1 photo exists.
Star Trek III The Search for Spock -
1980's TV version
Cuts off a great deal of the opening to fit in a time slot.
Star Trek IV The Voyage Home -
Many unfinished effects shots
Star Trek V The Final Frontier -
1990's TV Version
Cuts off most of the cat-lady and camping scenes
Star Trek VI The Undiscovered Country -
No known alternate unreleased version
Star Trek Generations -
Over 30 minutes longer than the theatrical version. Downloads can be found easily
1994 Preview Cut
Shorter, but contains the original ending, with almost fully completed effects. Lots of temp music.
Star Trek First Contact -
UK Theatrical Cut
Two extra scenes not seen anywhere else.
Star Trek Insurrection -
Workprints rumored to exist, never confirmed
Star Trek Nemesis -
Again, rumored workrpint. No confirmation
Well, that was healthy. Talk to you later.