All official scripting support is located at
-- in particular, the Introduction To and Scripting Tutorials are must-read for beginners, as they introduce the ID DOM with a couple of easy examples. After that, you can work through to the full Scripting Guide, where more difficult interactions are explained (again with lots of basic building block examples).
Versions of these documents can also be accessed through the ExtendScript Toolkit Editor (ESTK) that got installed along with your InDesign, and are available in the Help menu.
If you're confident you can find your way around the DOM, you can graduate to using
1. ScriptUI, for almost-but-not-quite native looking interfaces: http://www.kahrel.plus.com/indesign/scriptui.html
2. The Compleat InDesign JS Reference: http://www.jongware.com/idjshelp.html
(the latter being of my own hand, a more comprehensive overview of DOM relations than Adobe's own. also viewable on-line, courtesy of mr. John Hawkinson, at http://jongware.mit.edu and subfolders therein).
.. of additional interest:
Marc Autret's site: http://www.indiscripts.com/ -- lots of interesting (very advanced) topics and the occasional Scripting Forum Roundup, where he lists noteworthy snippets, at times illuminated with his own professional commentary.
There used to be a quick link to a list to all kinds of resources somewhere around here, but either it fell into disuse or has fallen victim of one of Adobe's forum-wide "updates" (har, har). Perhaps someone can retrieve it?
I just wanted to thank you both for providing all these great ressources. I will probably go through some of them myself.
That been said, the first person we had hired called us the Friday before starting and quitted the job for family reason (I hope he's find). Fortunatly, we had another person in mind and since then he started working here, but he didn't have any experience with inDesign at all. So right now, he is getting familliar with the environement and we asked him to follow some courses on Linda.com to get familliar with the software first.
Again thank you and have an Happy New Year!