I have been using Linux as an embedded operating system since 1999 and as a desktop operating system since about 2003. My main interest is getting Linux to work on various devices such as phones, set-top boxes (*), printers, etc., etc.
There are some tutorials on aspects of using Linux as an embedded o/s in my blog called "The Inner Penguin", which can be found at http://www.embedded-linux.co.uk/
(*) Why set-top box? Have you ever seen one on top of a set? In most cases it would slide off down the back, becoming a back-side box.