The Beauty Department, a fantastic skin/hair/makeup website you seriously ought to be perusing weekly, recently posted on "mascara cocktailing." What is mascara cocktailing, you ask? Why, it's the combining of two different mascaras a la a cocktail. The point of mascara cocktailing is to get everything you could possibly want out of a mascara: Length and volume; definition and no clumps; etc. Mascara, like everything in life, is not one size fits all, so by combining two (or more, if you're feeling crazy), you're getting exactly the look you want.
The Beauty Department named a few of their favorite combos -- Kevin Aucoin Volume + Blinc for volume and length; Maybelline Full 'N Soft + Lancome Definicils to thicken and separate; and CoverGirl Flamed Out + Tarte Gifted Smart Mascara to wing out and intensify -- but it's definitely worth it to try out a few on your own.
And mascara isn't the only makeup you can "cocktail."