It took a while to find an easy-to-use free resource editor that works smoothly with Mac OS X. With the help of a friend from Iceland, here is the hint: get a copy of Rezilla 1.1. For what I need it for, it works perfectly.
[robg adds: I haven't done much with resource forks at all since OS X came out, but for those who need it, this looks like a decent replacement for ResEdit. The only other one I'm aware of is Resourcerer, but I'm not sure how current it is (and it's far from free).]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061210024357965