wkhtmltopdf and wkhtmltoimage are open source (LGPLv3) command line tools to render HTML into PDF and various image formats using the Qt WebKit rendering engine. These run entirely "headless" and do not require a display or display service.

There is also a C library, if you're into that kind of thing.

How do I use it?
Download a precompiled binary or build from source
Create your HTML document that you want to turn into a PDF (or image)
Run your HTML document through the tool.
For example, if I really like the treatment Google has done to their logo today and want to capture it forever as a PDF:

wkhtmltopdf http://google.com google.pdf

In this tutorial we will show you how to create and use a thumbnails preview slider with jQuery. Since we got a lot of requests to show how to make the preview slider work separately from the full image view, we decided to make a tutorial on how to use the little thumbnails preview part only.