I'm a Clojure guy, but the ML family (specifically OCaml and F#) have always interested me as another branch of functional programming. I started out in the before times as a .NET Programmer (VB6 -> VB.NET -> C#) and have toyed with F# a little since then. It's cool, but the tooling leaves a lot to be desired compared to what's available for OCaml unless you decide to use full fat Visual Studio.
What I particularly like about them is the middle ground of inferred types. I don't need types since maps, lists, and value types are enough for me in almost all cases, but if I must use a strongly typed system why not let the compiler figure it out for me? I always thought that was a neat idea.