Via the Clojure wiki I found a great page describing how you can use GNU screen and some Vim magic to let Vim play nicely with an interactive commandline program like a Common Lisp REPL, Ruby's
irb, or Python's, well,
That page is a very stripped-down and simpler version of what Limp does for Vim+Lisp. But Jonathan Palardy's version has the benefit of being so simple that you can set it up yourself manually in a second or two. I still have never gotten Limp to work quite right and I don't have the time to debug a big mess of Vim script.
The idea is to start up a named screen session via e.g.
screen -S foo -t bar, then start an irb session (or whatever) in there, and then in Vim you can simply yank some text into a named register and send it off to screen via a system call. Download Jonathan's code and see.
It's not a full-blown SLIME; it doesn't have tab-completion or weird interactive debugging windows or such bullcrap. It doesn't capture the output of your command and feed it back into your Vim buffer. But hey, it's pretty good for something you can throw together in 2 minutes, and it works.
So there goes my last reason to ever use Emacs. Good riddance, I must say.
Honestly, Emacs just frustrates the living hell out of me. Oh how I tried to like it. I really did. I've used it on and off constantly over the past year. I have Emacs shortcuts written all over the whiteboard in my office. But its braindead window management, its terrible broken undo/redo system, its finger-crippling key-chord combos, its lack of features I need (like line numbering), its reliance on broken 3rd-party elisp hack scripts for things Vim has built in (like line numbering!), its ugly fonts and GUI elements, and so on and so forth. Vim is such a joy in comparison.