The following MC's are from worlds not currently supported by TSR in mainstream D&D. they are largely fan-supported, and many of these monsters have been converted on official fan sites. i personally am not going to convert any of them, but i'm listing them all the same for matters of completeness.
MC4 - Dragonlance
Anemone, Giant
Avian (Emre, Kingfisher, Skyfisher, 'Wari)
Bear, Ice
Centaurs of Krynn
Disir
Draconian (proto-), Traag
Draconians (Aurak, Baaz, Bozak, Kapak, Sivak)
Dragon, Amphi
Dragon, Astral (Unmated, Mated Pair)
Dragon, Kodragon
Dragon, Othlorx
Dragon, Sea
Dreamshadow
Dreamwraith
Dwarf, Daergar
Dwarf, Gully
Dwarf, Hill/Neidar
Dwarf, Mountain/Hylar
Dwarf, Theiwar
Dwarf, Zakhar
Elf, High/Qualinesti
Elf, High/Silvanesti
Elf, Sea/Dargonesti
Elf, Sea/Dimernesti
Elf, Wild/Kagonesti
Elf, Half
Fetch
Fire Minion
Fireshadow
Gnome, Tinker/Minoi
Gurik Cha'ahl
Hatori (Lesser, Greater)
Haunt, Knight
Horax
Imp, Blood Sea
Kalothagh ("P rickleback")
Kani Doll
Kender
Kyrie
Lizard Man of Krynn (Jarak-Sinn, Bakali)
Man of Krynn (Ice Folk, Knights of Solamnia, Plainsmen, Rebels)
Minotaur of Krynn (Blood Sea Minotaur)
Ogre of Krynn (Common Ogre, Orughi)
Orge, High/Irda
Phaethon (Phaethon, Elder)
Shadowperson (Shadowperson, Revered Ancient One)
Shimmerweed
Skrit
Slig (also Ghaggler)
Spectral Minion
Spider of Krynn (Whisper Spider, Giant Trap Door Spider)
Tayling (also Taylang)
Thanoi ("Walrus Man")
Tylor
Wichtlin
Wyndlass
Yaggol
Yeti-kin, Saqualaminoi
MC7 - Spelljammer, volume one
Albari
Ancient Mariner
Argos
Astereater
Blazozoid
Chattur
Delphinid
Dizantar
Esthetic
Focoid
Fractine
Giant, Spacesea
Golem, Furnace
Golem, Radiant (The)
Gravislayer
Grommam
Hadozee
Jammer Leech
Lakshu
Lumineaux
Lutum ("Mud-Woman")
Mimic, Space
Misi
Moon, Rogue
Mortiss
Muderoid
Nay-Churr
Phlog-Crawler
Pirate of Gith
Plasman
Plasmoid, DeGleash
Plasmoid, DelNoric
Plasmoid, Ontalak
Puffer
Q'nidar
Rastipede
Reigar
Rock Hopper
Slinker
Spider, Asteroid
Spiritjam
Survivor
Syllix
Symbiont
Vine, Infinity
Wiggle/Hurwaet (Hurwaet, Swamp Wiggle, Salt Wiggle)
Wizshade
Wryback
Zard
Zodar
MC9 - Spelljammer, volume two
Alchemy Plant
Allura
Aperusa
Autognome
Bionoid
Bloodsac
Buzzjewel
Constellate
Contemplator
Dohwar
Dragon, Moon
Dragon, Sun
Dragon, Stellar
Dreamslayer
Dweomerborn
Fal
Feesu
Firebird
Firelich
Flowfiend
Gadabout
Gammaroid
Gonn
Gossamer (Standard, Noble)
Grav
Great Dreamer
Greatswan
Grell, Colonial (Soldier/Worker, Philosopher, Patriarch
Gullion
Insectare
Lhee (Common, Lesser, Greater)
Mercurial Slime
Meteorspawn
Monitor
Owl, Space
Pristatic
Scro
Selkie, Star
Silatic (Platinum, Gold, Iron)
Skullbird
Sleek
Sluk
Space Swine
Spirit Warrior (Spirit Warrior, Zwarth)
Sphinx, Astro
Starfly Plant
Undead, Stellar
Witchlight Marauders (Primary, Secondary, Tertiary, Space, Remote)
Xixchil
Yitsan
Zurchin
MC10 - Ravenloft, volume one
Bastellus
Bat, Ravenloft (Sentinel, Skeletal)
Bowlyn
Broken Ones (Common, Greater)
Bussengeist
Darkling
Doppleganger Plant (Plant, Podling)
Elemental, Ravenloft (Pyre, Blood, Mist, Grave)
Ermordenung
Ghoul Lord
Goblyn
Golem, Ravenloft (Bone, Doll, Gargoyle, Glass, Mechanical, Zombie)
Grim Reaper
Imp, Assassin
Impersonator
Lycanthrope, Werebat
Lycanthrope, Wereraven
Men (Abber Nomads)
Men (Lost Ones & Madmen)
Mist Horror (Common, Wandering)
Mummy, Greater
Quevari
Ravenkin
Reavers
Scarecrow, Ravenloft
Skeleton, Giant
Strahd's Skeletal Steeds
Treant, Evil
Treant, Undead
Valpurgeist
Vampire, Dwarf
Vampire, Elf
Vampire, Gnome
Vampire, Halfling
Vampire, Kender
Vampyre
Widow, Red
Wolfwere, Greater
Zombie Lord
MC12 - Dark Sun
Animal, Household (Hurrum, Critic, Renk, Ock'n)
Animal, Herd (Kip, Z'tal, Jankz)
Antloid, Desert (Dynamis, Soldier, Queen, Worker)
B'rohg
Banshee, Dwarf
Beetle, Agony
Bog Warder
Brambleweed (and Tree)
Burnflower
Cat, Psionic (Tagster, Tigone)
Cha'thrang
Cistern Fiend
Cloud Ray
Drake, Air
Drake, Earth
Drake, Fire
Drake, Water
Dune Runner
Dune Trapper
Elemental, Greater, Air
Elemental, Greater, Earth
Elemental, Greater, Fire
Elemental, Greater, Water
Elemental, Lesser, Air/Earth
Elemental, Lesser, Fire/Water
Erdland
Esperweed
Flailer
Floater
Giant, Athasian (Desert, Plans, Beasthead)
Golem, Athasian (Ash, Chitin, Obsidian, Rock, Sand, Wood)
Halfling, Renegade
Hej-kin
Id Fiend
Insect Swarm, Athasian (Locusts, Mini-kanks)
Kank, Wild
Megapede
Mul, Wild
Nightmare Beast
Plant, Carnivorous (Blossomkiller, Dew Fronds, Poisonweed, Strangling Vines)
Pterran
Pterrax
Pulp Bee
Pyreen ("Peace-Bringers")
Rasclinn
Razorwing
Roc, Athasian
Sand Bride (Sand Bride, Sand Mother)
Sand Cactus
Sand Vortex
Scrab
Silt Horror (White, Brown, Gray)
Silt Runner
Sink Worm
Sloth, Athasian
So-ut ("Rampager")
Spider Cactus
Spider, Crystal
Spirit of the Land
T'Chowb
Thrax
Tohr-kreen ("Mantis Noble")
Villichi
Zhackal
Zombie Plant
MC13 - Al-Qadim
Ammut
Ashira
Asuras
Black Cloud of Vengeance
Buraq
Camel (Desert Camel, Mountain Camel, Racing Camel, War Camel)
Camel of the Pearl
Centaur, Desert
Copper Automaton
Debbi
Dragon, Zakharan (Vishap)
Elephant Birds(Daolani, Djinnling, Efreetikin, Maridan)
Genie, Noble Djinn
Genie, Noble Efreeti
Genie, Noble Dao
Genie, Noble Marid
Genie, Tasked, Architect/Builder
Genie, Tasked, Artist
Genie, Tasked, Guardian
Genie, Tasked, Herdsman
Genie, Tasked, Slayer
Genie, Tasked, Warmonger
Genie, Tasked, Winemaker
Genie Double (Markeen)
Ghost Mount
Ghul, Great
Giant, Desert
Giant, Jungle
Giant, Reef
Hama
Heway
King of Birds (Simurgh)
Living Idol
Lycanthrope, Werehyena
Lycanthrope, Werelion
Markeen
Maskhi
Mason Wasp, Giant
Nasnas
Pahari
Rom
Sabu Lord
Sakina
Serpent Lord
Serpent, Winged
Silats
Stone Maiden
Zin