The applications for developing online help are expensive! Among the top application for developing online help is RoboHelp. However, RoboHelp is expensive enough to discourage the casual user.

For aspiring technical writers, trying HelpNDoc is beneficial. HelpNDoc is now widely used and becoming popular. Aside from it is easy to use, its free!

We have produced excellent online help using the free version of HelpNDoc.

Here's the publisher's description of HelpNDoc: