Check out this extensive list of links leading to exquisite 40k resources.
Ok, so I got this extensive list of various links around the Warhammer 40k RPG topic. All credit to LordFckHelmchen for providing this list!
"The Emperor Protects"
/r/40krpg Subreddit on 40k-related RPGs (contains some useful resources like maps, etc.)
DriveThruRPG Online store for RPGs (source for W&G ePubs)
Doctors of Doom Best place for W&G resources (Character forge, homebrew rules, threat library, ...)
Cicatrix Maledictum A (dead) blog with W&G resources
Tabletop to W&G conversion sheet Reddit post with help in converting threats from 8. Edition tabletop codices to W&G v2.1
Dungeon Painter Paid tool for map creation
Maps & Tokens
HB Token Builder (new version) Character token creator top-down & standing; actively maintained
Tangram Open-Source OpenGL Maps with different renderers (live & 3d). Useful for quick map hacks
/r/battlemaps Subreddit with (tabletop-focused) maps & related tips & ideas
Donjon Vast collection of very useful generators (names, dungeons, worlds, star systems, dice rolls, ...).
scifiideas Collection of (mainly) name generators
40k Gallery A collection of all sorts of 40k images with filters
Dataslates A collection of data slates to use for player information
Imperial parchment A collection of, guess what, imperially-inspired paper for player information
Female 40k chars A forum thread with a collection of female 40k characters
A 40k Author Blog of Robbie McNiven, a GW author, with lots of grim dark images
IG thread A collection of imperial guard images & fluff
Warhammer Art A website to buy fine-art prints, but also useful as inspiration
40k icons GitHub repo with 40k icons as SVG
Font guidance Reddit post with an in-depth guide for 40k roleplaying material from Black Industries & Fantasy Flight Games; TL;DR:
Requiem for headings (size 28)
Aquifer for subheadings (size 10)
IM Fell Great Primer Roman for text (size 8)
Jellyka Saint-Andrew's Queen for the faded scribbles behind headings (size 34).
40k fonts Forum thread discussing Warhammer 40k tabletop fonts
Dark Heresy fonts Forum entry on fonts used in the Dark Heresy series
Font identifier of myFonts.
Latex template for Warhammer 40k (Ork) codices (not actively maintained)
1d4chan Best 40k wiki because it takes everything with a grain (or more a ton) of salt
Segmentum Obscurus Wiki Small wiki dedicated to the Segmentum Obscurus
Heresypedia Small wiki for the FFG RPGs (Dark Heresey, Rogue Trader, Only War, Deathwatch, Black Crusade)