I was pointed at this by the MSHelp MVP Lead, it's a sweet little freeware app, works great. Within about 90 seconds of starting it, I had compiled my first CHM:
And they also have a blog, pretty nifty.
We use the Microsoft HTMLHelp Compiler and hand-crafted HTML. Although the compiler has the buggiest GUI I have ever seen in release software, actually it is not hard to author HTMLHelp files using this, hm, gem :)