Alternatives to Clojure

Other languages you might consider if Clojure isn't quite right for you:

Lisps:

• Racket: Learning functional programming in a Lisp (Scheme descendent from the most active Scheme group)
• Scheme: Some of these compile to C and Gambit has been used on the iPhone
• Common Lisp: Mature and powerful
• Arc: Paul Graham and Robert Morris's work towards a 100 year language

MLs:

• OCaml: Practical, fast, mostly imperative, and strictly typed
• F#: If you want to do functional programming on the CLR (.NET platform)

On the JVM:

• Scala: Non-Lispy alternative on the JVM
• A Common Lisp (ABCL) and a Scheme (Kawa) are available

Concurrent:

• Erlang: Distributed as well as concurrent

Hard core:

• Haskell: The purest functional language, lazy by default, increasingly influential

Popular:

• JavaScript: Very functional under the covers, now appearing on the server-side as well as in web-browsers (node.js), and getting faster all the time thanks to V8

Or not:

• With knowledge and discipline you can write in a functional style in other languages.  For example: Python (although the lambda is limited),  and increasingly in C# (especially with the addition of LINQ and lambda expressions)