Triple Sec, a clear, sweet orange-flavored liqueur, is an important part of any well-stocked bar. It is a component in many, many classic cocktails, starting with the venerable Fancy Whiskey cocktail.
Other orange liqueurs include Cointreau, Grand marnier, and the Curacaos (blue is most common, but you can get orange as well, and "white" (clear) seems to be extinct. Orange Curacao has a similar flavor to Triple Sec, but it is not colorless so it may not be an acceptable substitute if you want your cocktail to look as it should.
There are a number of common brands of Triple Sec, and most of them are little more than orange sugar-syrup suitable for pouring on orange sherbet. Two excellent brands that I have found are Stirrings and Marie Brizard. Lorna and I tried a side-by-side blind taste test of DeKuyper and Marie Brizard last night, and the latter won easily. It was interesting to note that the Marie Brizard Triple sec is not only stronger flavored, but at 39% alcohol it is much stronger than the common varieties. It also costs more than twice as much, but you don't need so much to get the same amount of orangey flavor, and it's a much better flavor at that.
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