OCaml: I like it, a lot. It's my current Favorite Language. I took the time to learn it a few years ago, and it was very, very mind-expanding. Having said that

OCaml: I like it, a lot. It's my current Favorite Language. I took the time to learn it a few years ago, and it was very, very mind-expanding. Having said that, there are a lot of constraints around real world use. Libraries, the ability to collaborate with other (blub) programmers, etc. I've used it exactly once in anger -- not on a learning/hobby project -- and although it was a resounding success, I had to go out of my way a bit even then to bring O'Caml to bear. I'd highly recommend it if you're out to learn, and particularly so if you've never used a modern statically typed functional language before. It also makes sense to deliberately choose learning projects that play to the languages' strengths. I myself set out writing a L-System interpreter & functional image composer, which is good for learning because you can see your bugs...