From the LA Times a "Master Class" on the vinaigrette:
Consider the vinaigrette, which I rate as the most under-appreciated sauce in existence. It is a sauce, after all, and relegating it to cold salads ignores its vast potential with fish and meat, where it can work as a marinade, as a braising medium and as a finishing sauce. Likewise, limiting yourself to the same old combination of red wine vinegar and olive oil misses out on the huge range of flavors achievable in a vinaigrette.Colicchio provides lots of information and options for spicing up a sauce that's really easy to make, but yet I almost never do. Something I should rectify.
Let's start with the basics. A vinaigrette is a mixture of acid, liquid fat and seasonings. Most herbs and spices are fat-soluble, which means their flavors really bloom in the presence of oil. Fat also provides the body necessary to help a sauce cling to the surface of foods. The function of the vinegar, in addition to dissolving aromatic compounds found in herbs and spices, is to brighten up a dish, adding a tangy counterpoint to earthy, rich or spicy flavors.
A traditional vinaigrette is a temporary emulsion — a finicky mixture of one liquid dispersed in another (in this case, oil in vinegar). The challenge with an emulsion is to combine two liquids that do not dissolve in each other. One way to do this is mechanically: use the force of a whisk or, better yet, a blender, to physically break the oil into millions of individual droplets.