You can try MS's latest half-hearted try
http://msdn.microsoft.com/vstudio/extend/helplite/
It's a crippled version of Innovasys HelpStudio.... I've never used it. I'd
never even heard of it until I saw the link in the Visual Studio 2005
"Latest News" Start Page.
Personally, I like MS's HTML Help SDK
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/htmlhelp/html/vsconhh1start.asp
It's straight and to the point... there's a learning curve though.
I've given Doc2Help
http://www.componentone.com/ multiple chances... once
many years ago and then again because it was offered for free with the
VB.NET 2003 Resource Kit a couple of years ago. I was hoping it had
improved. It had not... it SUCKS.
There's also RoboHelp. Haven't tried it in years.
http://www.macromedia.com/software/robohelp/ It looks sweet though if not a
little overlycomplicated.
I used to love creating classic Help Files using RTF in Word and then using
Visual Studio HelpWorkshop to compile them. I even had a great set of macros
to help me insert all the hyperlinks and table of contents and index and
keyword footnotes. Sadly, the newer HTML help is a little overcomplicated
(for what it does... which ain't all that different than classic WinHelp).
G' luck