I have never eaten nor even seen or smelled a truffle, nor am I likely to do so at their exorbitant cost. However, truffles fascinate me by their mystique, their cultivation, and the delightful sounding dishes prepared with a touch of truffles. Another reason for my consideration of truffles is as a possible cash crop for the small family farm. Inoculated tree stock can now be purchased from several places in the US, and will bear harvests in as little as 5 years. The harvests will increase with the maturity of the trees and can continue for decades.
Truffles belong to the fungal genus Tuber. “Truffles are the ‘fruit’ of fungi that live in mutually beneficial (ectomycorrhizal) symbioses with the roots of host trees. The truffle fungus explores the soil for water and mineral nutrients, which it passes along to the tree. In exchange, the tree provides sugars produced through photosynthesis to the fungus.” 
In France and much of Europe, truffles are found mainly in the roots of oaks. There is reported success in North Carolina of growing truffles in the common European hazelnut (Corylus avellana) inoculated with the fungus. In the Pacific northwest, they are using inoculated oaks (Quercus ilex, the holly oak, and Quercus pubescens, the downy oak) as well as hazelnuts and other species. Somewhere I read of success with birch but I have lost the reference. Generally the inoculated trees are planted and maintained as a ‘plantation’ or orchard. Yields per acre of 200-500 trees can vary from 25 pounds to 100 pounds, and like any farming operation, site selection, soil fertility and preparation, climate and orchard maintenance all affect yields.
Perhaps the best known truffles are the French black Perigord, Tuber melanosporum, and the Italian white truffle, Tuber magnatum. They fetch retail prices of between $1,000 and $3,000 per pound, with the white truffle being the more rare and expensive. It is estimated that the world market could absorb 50 times more truffles than France currently produces. There are now truffle-growing areas in Spain, Sweden, New Zealand, Australia, Oregon, North Carolina, Tennessee and the UK. 
White truffles were a favorite of the Emperor Claudius in ancient Rome, of Madame Pompadour in Paris, and of Marilyn Monroe.
“The truffle is the very diamond of gastronomy…”
- Jean Anthelme Brillat-Savarin (1755-1826), French gastronomic philosopher
- Rossini (1792-1868, The Barber of Seville and William Tell, etc.) defined truffles as the Mozart of the kitchen.
Because of their high prices, truffles are used sparingly. Truffles lose their distinctive aroma (said to be somewhat like sweet, fresh earth) very quickly and are often shaved raw at the table over salads, omelets and pastas or inserted as slivers in meats. They are found in foie gras, patés, and risottos. Truffle oil is sometimes used as a substitute but it is a chemical product and contains no truffles.
Many wonderful things are found below the earth. Some, like potatoes, are mundane and familiar to all. Others are extremely rare and most people live their whole life without ever seeing one. Such is the truffle. 
Beat three eggs with a touch of fresh ground pepper and a dash of water or cream (no salt until after cooking please; it causes chemical changes that toughen the egg).
The more thoroughly you beat the eggs, the smoother the omelet will be, and if you beat them to the point of fluffiness, the omelet will be very light and fluffy and should be cooked over slightly lower heat.
Fry gently in an omelet pan.
Option I: About 5 minutes before the end of the cooking, add sliced White truffles. Try adding them, waiting a minute and then turning off the flame and letting them sit for an additional few minutes to allow them to incorporate into the dish.
Option II: Add (in the last 30 seconds of cooking after the heat is off) Italian white truffle shavings. Top omelets with creme fraiche or unsweetened whipped cream.
Option III: Add sliced, peeled black truffles soaked in brandy right after the eggs have set slightly, a few minutes into the cooking.
Single black truffle: iStockPhoto.com/trufero, used by permission
Black and white truffles: iStockPhoto.com/anzeletti, used by permission
Some online sources for truffles: