A third-party tutorial about fman
fman user Richard Guay has graciously written an extensive tutorial:
fman: The Extendable File Manager for Any System
It explains fman's most useful features and how you can write your own plugins. In the tutorial, Richard uses his own ProjectManager plugin as an example.
I must say at this point that Richard has been an absolute star in the fman community. He contributed many plugins (which you can find in the list of plugins) and provided invaluable feedback that guides fman in the right direction.
Thank you Richard! :-)