I tried HelpMaker v7.4 Build 4, but for a "mature" product it is too buggy, even if it is free. For the life of me I couldn't get the table of contents to work in the HTML-Website option.
It does look like a lot of work went into the program, but from looking at the forums each release seems to break as many things as it fixes. Hopefully the forthcoming C++ version will fix these issues, but according to this post
HelpMaker won't be free for much longer. The reasoning is due to "personal attacks", which is the most bizarre reason I have ever heard of for going payware. If you want to charge for a product you've poured your heart and soul into go right ahead, but their reasoning is perplexing. They will just end up punishing the regular users of the program, who may look elsewhere when the free version is discontinued.
I ended up going with Helpinator 1.4 FREE
for my needs. It is limited to 10 topics (you can pay $99 for the Pro version that has unlimited topics) but 10 is more than enough for me. The interface is much simpler than HelpMaker, and supports CHM, PDF, RTF and Web as export options even in the free version.