A classic French sauce, and if you've never had homemade Mayo, you've never had the good stuff. I whipped up a small batch last night and topped some grilled chicken breasts with it, and it was awesome.
Put into a blender (or a bowl, if you are a masochist and want to use a whisk for this):
1 whole egg, and one egg yolk
2 teaspoons of lemon juice (ReaLemon works great)
A pinch of salt
1 pinch of ground mustard
1 teaspoon minced garlic (optional, but it makes it rock)
Blend on the lowest setting, and drizzle in up to a cup of oil.
For the chicken breasts I wanted to use the mayo as a sauce for, I blended it until it was still slightly non-solid. It can be blended until completely solid (solid isn't quite the term, but what I mean is like what you'd get in a jar at the store), but for the love of the FSM don't blended it past that point, or else it will break and you'll have a nasty mess (or so I've heard). Use it to top damn near any piece of meat, and if there are any leftovers, use it to make a salad the next day (the chicken salad I made with the leftover breast with the mayo and some celery was great).
Oh, and homemade Miracle Whip?
Miracle Whip ain't food.