Personally, I prefer Letter Gothic. It's slightly narrower than Courier and therefore fits more code on a line and I find it a little easier on the eyes.

update: If you're using Windows and have both Letter Gothic Line and Letter Gothic MT on your system, you may prefer Letter Gothic MT over the Line variant (which doesn't scale very well when using larger point sizes, even with font smoothing enabled).

If you like the Verdana font being used on many web pages, you might like a free font that Ray Konopka (a leading Delphi expert) provides on his web site. It's fixed-space and works quite nicely when projected across a room.

--f