All of this info was taken directly from the Bemani Guide as the site is currently offline, when the site comes back online this will be removed.
Remywiki - Generalized BEMANI content wiki.
GameRepair.info - Repository of arcade part repair & misc information.
Cons&Stuff - Community resource for DIY controllers.
BemaniPatcher - Drag and drop hex edit solution for most Bemani games.
sp12 - IIDX SP☆12 reference site/difficulty tier list.
iidx.insane.pe.kr - IIDX difficulty tier list.
Statistik - IIDX difficulty tier list.
atwiki - IIDX wiki in JP (includes tier lists).
textage.cc - Chart viewing resource.
DJ DAO IIDX troubleshooting guide - Step-by-step guide for FPS, FP7, PEE, RES, RED controllers.
sdvx.in - SDVX chart reference.
SDVX Progress Chart - Functions as a generalized tier list.
SDVX Unlock Guide - Translated guide for unlocks.
573Controller - DIY guitar solution for converting official cab guitars to USB home-use.
Drummania English Menu Translation - Handy for beginners, lots of options!