Ingredients: 1 1/2 oz light rum, 1 oz triple-sec, 1/2 oz lemon juice. Shake with ice and strain into a chilled glass.
Source: DIY Cocktails
This is basically a sidecar with rum instead of brandy. It was pretty good, but I think a daiquiri works better with the rum as far as cocktails of this type are concerned. Still, if I’m out of brandy, this will work in a jiffy. :)