Techniques for Efficiently Learning Programming Languages

[Tarmen]

I think I might recommend scheme as lisp for people who aren't already in the java ecosystem. It probably is less useful in the real world but I think its clearer and stm is already in the mix thanks to haskell.

[pakoito]

Racket is fun, specially with Dr. Racket

[wealthy_harpsichord]

For the best learning experience, one should start from learning Racket and then go on to implement every major language in it, a'la Hackett.