Cook bacon in a large skillet until crisp; remove bacon, reserving 1/2 cup drippings in skillet. Crumble bacon, and set aside.
Sauté onion in drippings until tender. Add beans, vinegar, salt, and pepper. Cook over medium heat until thoroughly heated. Remove from heat. Cover and refrigerate at least 3 hours.
Combine bean mixture, almonds, and crumbled bacon in a large saucepan. Cook over medium heat until thoroughly heated. Transfer to a serving bowl.