IBM has published another article in their alt.lang.jre series, this time on JRuby. JRuby is a pure Java implementation of the Ruby language. Ruby is often described as an object-oriented scripting language, and it combines the pure OO features of Smalltalk with powerful scripting features along the lines of Perl or Python.
I have used various scripting languages (mostly Perl and Ruby) here and there, but never long enough to really become proficient in any of them. I have been planning on learning Ruby for a while, and with the availability of JRuby, it now becomes a powerful extension mechanism for Java, and learning it would definitely be a worthwhile investment.
Of course, Groovy is a strong contender as well, and in fact it borrows many features from Ruby. It seems to have a slight edge when it comes to Java integration, but can be used as a standalone scripting language as well. Then again, Ruby has the advantage that it is more lightweight as it does not require a JVM (unless of course you want to use JRuby).