This is a really nice one... released by MS:
Sandcastle - http://sandcastle.codeplex.com/
Capable to output HTML (with ASP.NET files so that you can deploy to IIS with more feature), HTML Help 1.x (.chm), and HTML Help 2.x (.HxS).
And you would probably like this nice GUI of the tool:
Sandcastle Help File Builder (SHFB) - http://shfb.codeplex.com/
There is also a Visual Studio integration:
DocProject for Sandcastle - http://docproject.codeplex.com/
It's powerful but I like the SHFB more for simplicity :)
Some notes to add:
- Remember to read the instructions for SHFB before installing and you will find prerequisites like the Microsoft HTML Help for outputting .chm files.
- Simply specifying the solution files in SHFB will do the job - don't really need to add all source files!
- You may need to reconfigure your C# projects so that it also generates XML document files when building, or else the method/field descriptions will not be available in the output.
- If you encounter errors when generating the output, try to change the Working directory in SHFB settings to something really simple - alphanumeric onlys, without spaces, etc (something like C:\Temp\working might be a good one)... It seems that the hhc.exe from Microsoft HTML Help packages does not handle special characters well...
That's it. Enjoy!