F# is very similar to OCaml, which is already supported.
As it will be shipped with Visual Studio 2010, F# will be more and more popular.
Project Euler is a good source to practice F# (http://fsharp-euler.wikispaces.com/), but the problem style there is limited. It would be very helpful if SPOJ adds a support for F#.
BTW, F# could be running on Mono platform.
Thanks!
