For Lisp, I found using Scheme and reading The Little Schemer and SICP more helpful than PCL. I've also been using and heavily customizing Emacs, but Emacs Lisp

For Lisp, I found using Scheme and reading The Little Schemer and SICP more helpful than PCL. I've also been using and heavily customizing Emacs, but Emacs Lisp is kind of a crappy Lisp, and keeping track of its idiosyncrasies while also learning Scheme or Common Lisp's will probably be really confusing initially. Scheme is also a lot more my style than CL, though. YMMV. I also found learning OCaml to be a real eye-opener, both for learning FP techniques (it emphasizes a different set of them than Lisp) and how to work with, rather than against, static typing. (_The Little MLer_ helped, as well, and is at least as good for learning types as _The Little Schemer_ is for recursion, IMHO. Highly recommended.) There's not a whole lot of material published in English on OCaml (the Joshua Smith book is terrible!), but there's a translation of a French O'Reilly book online (http://caml.inria.fr/pub/docs/oreilly-book/ http://caml.inria.fr/pub/docs/oreilly-book/), and it's quite good for learning the main ideas. The first few chapters are on functional programming, imperative programming, and then their relative strengths & when to use each. (Their emphasis on using FP when appropriate, rather than treating it as the new best thing ever, suggests more insight to me than the blind enthusiasm for languages that tends to cycle through here and reddit.) Also: OCaml is not without its flaws. In particular, its errors can be cryptic, and it's standard library has some infuriating omissions. The language is fantastic for some kinds of problems (ML's forte is anything involving complex data structures), though, and it's a great way to learn some very useful techniques.