This list is huge so I'm just going to put the actors/actresses and their roles:
Chris Evans-Steve Rogers/Captain America
Robert Downey Jr.-Tony Stark/Iron Man
Scarlett Johansson-Natasha Romanoff/Black Widow
Sebastian Stan-Bucky Barns/Winter Soldier
Anthony Mackie-Sam Wilson/Falcon
Paul Bettany-The Vision
Don Cheadle-Jim Rhodes/War Machine
Elizabeth Olsen-Wanda Maximoff/Scarlet Witch
Paul Rudd-Scott Lang/Ant-Man
Chadwick Boseman-T’Challa/Black Panther
Emily VanCamp-Sharon Carter/Agent 13
Frank Grillo-Brock Rumlow/Crossbones
William Hurt-General Thaddeus “Thunderbolt” Ross
Holy Crap that's a huge cast! Now there are some actors/actresses who are in it and doesn't have roles just yet:
Martin Freeman and Daniel Brühl.
What do you guys think of this cast?
Source: http://marvel.com/news/movies/24586/marvel_studios_begins_production_on_marvels_captain_america_civil_war