This may come off as blatant e-whoring (and if it is, please purge the thread), but I want to share what I've got with you guys.
I'm running a relatively new in-character 40k lore blog: The Inquisitorial Archives ( http://theinquisitorialarchives.tumblr.com/ ). It's a little pet project of mine, inspired by the various references 'cited' in the Ciaphas Cain books. It's presented as a series of extracts from various texts and documents written by acolytes, all collected by Inquisitor Hector Grammun. I also post character bios (expect a series of Inquisitors in the next week or two, along with some other NPCs).
Feel free to submit requests! I'm eager to answer them and hopefully it'll inspire me to update more.