Blu-ray and SteelBook:
Blu-ray.com: The ultimate Internet reference when it comes to Blu-rays
SteelBook.com: The official website
SteelBook⢠Hunterz: A homely forum where one can discuss about SteelBooks, both DVD and Blu-ray
Blu-ray Region Code Info: Need the region coding to a Region A, B or C release? Here’s the place to go
Hi-Def Release Lists: This website has an extensive listing of all current and upcoming Blu-ray releases worldwide
BluSteelBook: References all the SteelBook Blu-ray releases worldwide, sadly not as up-to-date as the list I’ve gathered 
Other cool places:
EXCLUSIF: A forum about all sorts of collections