Place bacon in a large skillet. Cook, turning frequently, over medium high heat until evenly browned. Cool, and then crumble.
Preheat oven to 300 degrees F (150 degrees C). Spread slivered almonds on a cookie sheet. Bake for approximately 12 to 14 minutes or until lightly browned, turning once during toasting. Cool.
In a small bowl, mix together mayonnaise, sugar, and vinegar. Set aside.
In a large bowl, combine broccoli, crumbled bacon, celery, green onions, red onions, grapes, and toasted almonds. Toss with mayonnaise dressing. Chill for several hours in the refrigerator.
