Java clustering with Terracota is a popular option given its open-source roots. This post by Paul Stadig takes a look at the benefits of using Clojure -- a LISP-like Java compatible implementation -- to underpin a Terracota application. Read Paul's post 'Clojure + Terracotta = Yeah, Baby!': http://paul.stadig.name/2009/02/clojure-terracotta-yeah-baby.html