Have a look at the L4 user manuals on http://l4hq.org/docs/manuals/
They contain plenty of sample code and explanation, although not for the latest versions. Examples for OKL4 v 2.1 can be found on my Advanced Operating Systems lecture slides, "week 2", se http://www.cse.unsw.edu.au/~cs9242/10/lectures/
Gernot