I decided to start learning Lisp, after hearing good things about it from a bunch of people. So far, I can recognize a lot of Ruby elements that must have been ganked from Lisp. My prediction is that Ruby will end up being mostly a superset of Lisp except for a few areas Lisp is specifically targetted at. But we'll see.
I'm learning right now via the book Practical Common Lisp. The whole thing is free online, which is clearly awesome. I may buy it just so I can read it when I'm away from my computer.
As the book says, finding a Lisp interpreter isn't straightforward, because there are a lot of them. I settled on SBCL, for the simple reason that it's the only one that would compile properly. If you use Gentoo and want SBCL, be sure to get the unstable version. The stable version wouldn't even compile for me.
I'm resisting the push to use emacs instead of vim. I'll stop using vim when you pry it from my cold, dead hands.