It's easy to make limoncello - just cover lemon peels with 100 proof alcohol for a few weeks, then add simple syrup to dilute and let sit for another week or two. This eGullet thread answers some question and gives a recipe and tips for making it on your own.
Whether you make it yourself or purchase it, limoncello is good for more than drinking. Its intense lemon flavor is wonderful in baking and summer cooking - here's a few recipes we'd like to try...Nick Malgieri always has splendid recipes. Try his yeasted cake with limoncello syrup: Limoncello Baba. The liqueur lends itself very well to frozen desserts, too - try this Raspberry Limoncello Semifreddo - it looks beautiful! This moist Torta di Limoncello looks amazing, too, and we're dying to try this ricotta pudding with limoncello.
If you decide to just drink your limoncello, remember it is always served icy cold. Try this Limoncello Collins.