Obviously, with their deal with Sony, the situation has changed in regards to them, but this was a list of characters whose right Marvel had sold away as of a while ago:
20th Century Fox
Fantastic Four: Doctor Doom/Victor von Doom, Human Torch/Johnny Storm, Invisible Woman/Susan Storm, Mr. Fantastic/Dr. Reed Richards, The Thing/Ben Grimm, Nova/Frankie Raye, Alicia Masters, Willie Lumpkin
X-Men Mutants: [Agent Zero/Maverick/David North], Angel/Warren Worthington III, Arclight/Phillippa Sontag, Beast/Dr. Henry Phillip Hank McCoy, [Blob/Frederick J. Dukes], [Bolt/Christopher Bradley], Callisto, Colossus/Piotr Nikolaievitch Rasputin, Cyclops/Scott Summers, [Deadpool/Wade Wilson], Emma (Grace) Frost, Jean Grey/Phoenix, Juggernaut/Cain Marko, Gambit/Remy LeBeau, Glob Herman/Herman Gardner, Iceman/Bobby Drake, Jubilee/Jubilation Lee, Katherine Kitty Anne Pryde, [Kestrel/John Wraith], Lady Deathstrike/Yuriko Oyama, Leech, Magneto/Erik Magnus Lehnsherr, Mastermind/Jason (Wyngarde), Multiple Man/James Arthur Madrox, Mystique/Raven Darkholme, Nightcrawler/Kurt Wagner, Phat/William Robert Billy-Bob Reilly, Professor Charles Xavier, Psylocke/Elizabeth Betsy Braddock, Pyro/St. John Allerdyce, Quill/Max Jordan, Rogue/(Anna) Marie, Sabretooth/Victor Creed, Sebastian Hiram Shaw, [Silver Fox], Siryn/Theresa Rourke Cassidy, (The) Spike, Storm/Ororo Munroe, Wolverine/Logan
X-Men Non-Mutants: Drake Family (Steven, Madeline, Ronny), Grey Family (Dr. John, Elaine), Henry Peter Gyrich, Robert Edward Kelly, Dr. Moira Kinross MacTaggert, Dr. Kavita Rao, William Stryker, Bolivar Trask, Warren Worthington II
Sony Pictures
Spider-Man: Spider-Man/Peter Parker, Doctor Octopus/Otto Octavius, Green Goblin/Norman Osborn, (New) Green Goblin/Harry Osborn, [The Lizard]/Dr. Curt Connors, Sandman/Flint Marko, Venom/Eddie Brock Jr., Betty Brant, Dennis Carradine (Buglar), J. Jonah Jameson, Ben Parker, May Parker, John Jameson, Joseph Robbie Robertson, Gwen Stacy, Mendel Stromm, Flash Thompson