An excellent recipe for kahlua (I learned this from some friends of mine in Chapel Hill, NC; thanks Ross):
Heat 6 cups water, mix in 3 cups of sugar until it is completely dissolved. Remove from heat, mix in a half cup of coffee crystals and 2 ounces of vanilla extract. Let cool and mix with 1/4 gallon of 100 proof vodka (the better, the better). Experiment with the proportions to taste.
This kahlua not only tastes really good, but also gets you wired :).
I suggest mixing this with orange juice, about equal parts of each. You'll be surprised at the taste.