Display help file in your application

How do you, or what do you use to create/display your help files in the applications you develop?

I am building an application and debating how i will do this?

Looking for ideas, what others are doing.

context sensitive, simple pdf, popup with frame (TOC to the left, content to the right), etc…

Depend on context of your help. For example, for field help in form you can add help text to your model, refer to attributeNames() function for the idea.