I am learning Clojure and I like it. Following the ThinkRelevance functional koans has given me a really good interactive playground for learning this language. Reading through examples in a book cannot compare to actually having to write code in order to solve a problem and in the process learn syntax and the rules of a language. What a concept!
I came across something in the sequence comprehensions section that I thought was interesting.
The "for" macro can loop over one (or more) groups of things and produce the vector combinations above. I was reminded while reading this of Ruby's Array#product method, which does the same thing (return the product of 2 or more arrays).