By way of ligfiets.net I've found a Dutch website with a lot of commentary on bicycle accessories, and by all accounts the author is trying to offer genuine information and testing which the magazines apparently don't. A starter for ten is on lighting, specialising in dynohubs and beam shapes (at some length!):
http://swhs.home.xs4all.nl/fiets/tests/verlichting/index_en.html
Carry on and you find a whole index of review subjects for saddles and pumps and multi-tools and tyre levers and all kinds of things.