Here is a great recipe from Bon Appetit Magazine–I especially love the added mint:
Mix 2 cups finely diced peeled cucumber. 1/2 cup finely diced red onion, 1/4 cup chopped fresh cilantro, 1/4 cup chopped fresh mint and 1 finely diced jalapeno (with seeds) in a medium bowl. Stir in 3 Tbsp. fresh lime juice and 1 Tbsp. vegetable oil. Season to taste with Kosher salt, freshly ground black pepper and more lime juice. Makes about 3 cups.