This year's JavaOne had an interesting competition... the Script Bowl. Pitting 4 different languages (Groovy, Scala, Jython & JRuby) on the JVM against each other in three different categories. (Rich Client Application, Web Application and an Open event) Check the results here on Rags' blog.
Headius just posted the JRuby Script Bowl artifacts for your viewing pleasure. Anyone know if the other languages have posted their apps/code?