If you're interested in actually checking these out, 7 Languages in 7 Weeks (http://pragprog.com/book/btlang/seven-languages-in-seven-weeks http://pragprog.com/

If you're interested in actually checking these out, 7 Languages in 7 Weeks (http://pragprog.com/book/btlang/seven-languages-in-seven-weeks http://pragprog.com/book/btlang/seven-languages-in-seven-wee...) covers five of these (Haskell, Scala, Io, Clojure, Erlang) as well as Ruby and Prolog (Prolog is my favorite language from the book, oddly missing from this list). Apart from being a very good introduction to syntax, it teaches you the unique features of each language and why you should care about it. Highly recommended.