Do you know a good tutorial for OSGi? It should describe in detail how it is used, but also how it works internally, as well as various implementations and their differences.
A very good way to get started with OSGi as it was designed is with bndtools. See http://bndtools.org/doc/tutorials/components/ for more information.
I personally can recommend OSGi and Equinox (the focus is on Equinox). I have not read it myself (yet), but OSGi in action looks promising.