There are three possibilities to offer documentation or help with Eclipse: as an integrated help system of an RCP application, as a standalone help application (which could be used for non-RCP applications) or/and as a so-called Infocenter web application.
(Graphic is based on this HERTZ add)
There are a couple of reasons why the company that I am working for chose Eclipse as their help system: it runs on both Linux and Windows, it scales (even with thousands of topics), and it just works although it is based on the outdated version of Lucence. And there is one feature that I have not seen in other help applications so far: the help content can also be produced on-demand. For example if you want to include text or data entered by users or show different help content depending on the configuration of your application. Like the static content the dynamic content is single-sourcing, this means that you have to write it only once for all platforms and all three deploy possibilities described above. That’s pretty cool.
But there is also a feature I’m missing (see bug 315013): in the Infocenter the URL does not follow the navigation between topics. In order to deep-link a topic, the topic link in the TOC has to be used instead of the web page URL.
In order to reference to a search result you have to use the parameters tab and searchWord, e. g. http://help.eclipse.org/galileo/index.jsp?tab=search&searchWord=HELP!!! shows the Eclipse Galileo search results of HELP!!! This makes it possible to define a Web Browser Search Engine Plug-in for Eclipse Galileo help or for your own Infocenter.