Hi Walt,
I'm using Haskell (GHC and Hugs) on several different platforms. Windows, OS X and Linux systems.
Assuming that you want your students to be able to use any of the above platforms, the only options I know of which work well on all of the platforms are Emacsen, Vim, hIDE, Eclipse and JEdit.
I'd like to have an IDE that works well for medium to large size projects. I know of Eclipse and hIDE. Vim works fine but I'd like more. hiDE seems to be "in process."
Much as I love Emacs, I can possibly imagine that you'd prefer to spend the course teaching Haskell, rather than how to use your editor. I personally found Eclipse very difficult to get on with, although YMMV. Although I don't use it much any more, I found JEdit to be very straightforward to use (very good menu-based GUI, plenty of features, syntax highlighting for most languages any sane person could want, and generally very easy to pick up). It's very underrated IMHO. The main reason I switched is that it does slow down with lots (>20, some very large) of files open. Emacs is better with very large projects (I mean > 10,000 files here), which is why I use it. I'd recommend it as a very good editor / simple IDE for people who don't want to spend their life learning to use their editor... HTH Regards Jeremy