I've used Slime within Emacs as my primary development environment for Common Lisp (or Aquamacs on OS X), but are there other compelling choices out there? I've heard about Lispworks, but is that [or something else] worth looking at? Or does anyone have tips to getting the most out of Emacs (e.g., hooking it up to the hyperspec for easy reference)?
Update: Section 7 of Pascal Costanza's Highly Opinionated Guide to Lisp give one perspective. But to me, SLIME really seems to be where it's at.
The most pleasant way I have found of accessing the Common Lisp standard is through Info. Build and install the Info files as described on http://www.phys.au.dk/~harder/dpans.html. Then add the following to your ~/.emacs.el:
(require 'info-look)
(info-lookup-add-help
:mode 'lisp-mode
:regexp "[^][()'\" \t\n]+"
:ignore-case t
:doc-spec '(("(ansicl)Symbol Index" nil nil nil)))
You can look up the symbol at point with C-h S.
Depends on the which Lisp, you may be referring to Common Lisp.
A very minimalistic but useful Lisp IDE for Windows is "LispIDE" available from:
Simple, effective and free.
There is a Lisp IDE available with Clozure Common Lisp (née OpenMCL). It looks fine, although I like SLIME better. Clozure, however, is the bees knees: an order of magnitude faster compilation and execution on a 64 bit Intel Mac, and a better "user experience" in general. Look around on common-lisp.net for Rittweiler's new slides on using SLIME, they're very helpful.
I use Vim, the Ion3 window manager and terminal windows and enjoy it very much.
I'll second the clozure common lisp IDE on MacOS/X. You'll remember it fondly if you ever used Macintosh Common Lisp. They are working to improve it, and, bonus, you get compete source.
In addition, if you just want lispish, dr-scheme has quite the IDE as well.
I'm very late on this, but it's strange that nobody has mentioned the LispWorks IDE here, and it even has some GUI-Builder, which is portable across platforms (minus Mac OS X).
Also if you want a whole operating system for your Lisp programming undertaking, there still does exist Open Genera (which just runs on Dec Alphas (who is currently the owner of DEC ;-(), it's a complete OS written in Lisp and even has a C compiler, implemented in Lisp AFAIK, targeting the OS. It's very strange. You'll find a few things which we nowadays take for granted. E.g hyper referenced documents (but this was before the Web). It has a few "Lisp" dialects and the base is ZetaLisp, but Common Lisp works. All the tools and things can be introspected during runtime. It's a very strange feeling.
However, I just mentioned it. I guess nobody here will ever have touched OpenGenera....
@Charlie Martin: (not enough rep to comment, yet)
The 41-slide December 2008 talk is at http://common-lisp.net/~trittweiler/talks/slime-talk-2008.pdf. There's an additional 8-slide 2009 lightning talk at http://common-lisp.net/~trittweiler/talks/slime-lightning-talk-eclm-2009.pdf.