Closures are programming language constructs that have been around about as long as programming, but the prospect of their inclusion in future versions of the Java language has stirred up all manner of controversy.  This talk aims to demonstrate how closures work in many different programming languages, including modern JVM-based languages such as Groovy, JRuby, and Scala. We will also explore closures in Smalltalk, Scheme, JavaScript, C#, and the BGGA prototype for closures in Java. After the talk, the participant should have a keen sense of how to use closures to eliminate repetitive code and write more natural, concise, expressive code using closures.