[Phalanx]

Make mayonnaise?
What's mayo? Well...I don't know what the hell the shit is they sell in most jar nowadays, but it's not quite right. Mayo is known as a "cold emulsion", I guess how you'd descrbe that, would be "two things that don't normally mix, with an added agent to make it into a permenant bond"? (eg - In this case, oil and vinegar. Eggs, or rather, the lecithin, a protein in the eggs, is the emulsifying agent, and makes a significant part of the mass here.)
It's also one of the 6 "mother" sauces, which are basically the buiding blocks for a whole hell of a lot of derivative sauces.
Anyways...

Get a large glass bowl and a whisk (or electric beater if you want to cheat, as "they" say, or yknow...not kill your wrist, as I say.)
I personally use a whisk, but the first few times doing this are a bitch.
Put a damp tea-towel under the bowl to stop it from slipping.

Get four eggs, and crack em into the bowl.
I personally only use the yolks, but you can keep them whole, your choice.

Get a 2/3 full tablespoon of white vinegar, or white wine vinegar, and whisk that into your eggs...gently, not enough to make it all foam up.

When that's done, whisk continuously while adding oil at a slow, even pace.
don't just pour the oil in alltogether or you'll fuck it up, you have to give the ingredients time to bond with eachother. As you continue pouring oil, whisk vigerously. The mixture will become thicker as you go.

Get it to the consistancy you consider appropriate (no exact amount of oil, it depends on how you want it), then season with salt, and white pepper, to taste.

If the mixture is too thick for your liking, some lukewarm (not hot) water added will thin the mixture. Be careful when adding.

That's you're basic Mayo.
A few derivatives...for all of these, start with the base mayo.

*Dijonnaise - Pretty simple, just add dijon mustard.

*Tartare sauce - Add chopped pickle (gherkin, whatever you call it), some lemon juice (whisk it in immediately), some chopped garlic, and a little horseradish.
**I like adding a few drops of tobasco to mine, just a little finely chopped spanish onion for texture, and a few capers as well.

*Caesar Dressing - Thin it down a little with some lukewarm water.
Add Dijon mustard, a little wholegrain mustard, garlic, lemon juice, worcestershire sauce (not too much), some grated parmesan cheese, and a few chopped anchovies - Either blend this one, or make sure you chop/grate everything up finely. You can add more salt and/or pepper, but if your base mayo is seasoned properly, you shouldn't have to.

I know I haven't given exact quantities, as I never use them myself...you've got to just work out how much of a flavour you like personally. Taste it as you make it, and you can't go wrong by yourself.

There ya go...this stuff's much better if you make it at home.