To some it might be obvious, for me it sure wasn’t : how to convert a series (sequence) of rendered frames to an AVI movie. There is a way to do it in the Video Sequence Editor (http://wiki.blender.org/index.php/Manual/Using_VSE#Add_Movie_and_Image_.28Stills_or_Sequences.29)
But I find it easier (although less versatile) to do it w. compositor nodes. It might have been documented elsewhere, but I made a reminder for myself with a sample .blend and some step by step walkthru: http://www.swineworld.org/blender/tips/
This might be usefull for someone else as well.