Ask HN: Good examples of user guides?

I'm creating a user guide for a SaaS application. We've done the plain-old-PDF versions before. I want to do something different and better. Does anyone have any good examples I could use for inspiration?

I know basic HTML/CSS and can figure stuff out, but I'm not a web developer so I'm not looking to build anything crazy. I should probably also mention that the users are tax professionals and are not particularly tech savvy individuals (understatement).

We offer an knowledge base widget that you can add to any page of your existing website and inherits your design and blends into. You can check it out at http://userdeck.com/guides and if you have any questions or feedback, I'm all ears!

Have you asked your users what format would they like the user guide in? If your users are okay with PDF, then stay with it. In the end, user guide and its format is for users, and not for you. Unless, users are requesting or indicating preferences for different format, I will suggest focus on other tasks.

Personally, for user guides, I prefer PDF. It keeps the formatting and the order. I can markup the PDF with my notes and highlights. I can download and keep a copy. Wiki (information dump with no specific order of reading), FAQ (answers to most often asked questions) and knowledge base (answers to one off/unique situations) are different tools for different purposes and don't necessarily address user guides in a nice way.