A link by Arvid led me to Dzone, where I found their "refcards": http://refcardz.dzone.com/ and after 15 minutes of reading, a lot of things, like file structure of Eclipse plug-in projects, had became much clearer.
For anyone new to Bioclipse plugin development, I think the following ones are the most relevant (especially the first two):
You will have to register at the site, and browse through the available ones in order to find them