[a] — eyes open

Slackware
The oldest linux distro that's actively maintained. Uses rc.X scripts to get things done, unlike most who joined the dark side. This is my daily driver at home. Slackware has a wonderful community at everyone's favorite LQ. They also have a wiki and a guide where you can read everything slackware related.
OpenBSD
The *nix for those paranoid with security. It's reputation in it's realm is unparallelled. OpenBSD is usually branded as a server OS, but many have it running on their desktops and laptops. And btw it's man pages are unmatched in quality.
The Linux Documentation Project
Excellent collection of tips & tricks, guides and everything you'll need with linux. My first steps in bash were with tldp's help.
Arch wiki
I was for a long time an archlinux user and their documentation was the reason. It has topics ranging from installations, desktop customizations and even server-related stuff. The wiki maintaners and writers are a good bunch. I always return to the archwiki, when my google-fu fails me.
LinuxBBQ
The grill where everyone is welcome. They roll out Debian with just enough meat and home-made spices. I learned / still learning a lot from here. The members are all masters with their linux-fu. Join them, and you'll wish why you haven't looked at the source, all this time.
nixers
A community for *nix enthusiasts and hobbyists.
bunsenlabs
The official sucessor to #! linux, that started the minimal desktop ricing frenzy. The infamous #! community lives on through bunsenlabs. #! made editing config files fun. And when you bork the system, a community member would already have the answer to the problem.
Programming Motherfucker
Averaging 31 "fucks" per paragraph, this site is an indispensable resource for every beginner-programmer. The python bit me here, which is also the work of the main guy behind this site.
Dotshare
What's life without dotfiles?
Daemon forums
A forum for everything BSD.
xero
His website speaks for itself.
z3bra
Work flow grokker and supreme overlord. His blog is pretty sweet and always to the point. His screencasts are the reason why I switched to vim.
alienbob
This is a veteran slackware user's blog. He puts up top notch packages and his writings are excellent. I use his repo for most of my linux binaries.
vermaden
The one man army in BSD land.
Abraham Sankutty
Demystifies CSS for fun. He is my mentor and good friend.
venam
The webmaster at nixers, he does interesting podcasts and is the author of 2bwm.
P.K Murugan
The man who made BSD cool (atleast for me). His blog posts are epic and his unixporn collection is well known. The blog has been dormant since 2013 though.
arpinux
The author of the now defunct livarp. The site may be in french, but if you know how to look, you'll get what you want.