Capwolf

In one of the worst Captain America story arcs ever, Captain America and guest-stars Dr. Druid, Werewolf By Night, Wolverine, Cable, and Wolfsbane take on Nightshade, a pack of werewolves, and the Starwolf.

Revolutionary War Captain America

An ancestor of Steve Rogers used this costume in the dawning days of American History (since this occured in CA: SOL which had several 'imaginary' stories, I'm not sure if this is actually from the Marvel Universe or not...).

American Dream

From the A-Next universe, this lady (named Shannon Carter) brought grace, athleticism, and tenacity to the legacy of the Shield.

Super-Soldier

From the Amalgam Universe, a cross between Captain America and Superman.

Yeoman America

Captain America and the Avengers trapped in Morgan Le Fay's medieval fantasy world.

Captain America Jr.

An Amalgam Universe mixture of Captain Marvel Jr. and Captain America.

Ultimate Universe Captain America

More ruthless, more of a professional soldier than the Marvel Universe Captain America, this version seems to have all of the combat skill and strategic knowledge, but none of the soul and compassion.

Commander America

From an alternate future.

Captain Kree

From Fantastic Four, volume 3 #16.