Here are some links I labeled as “usefull” ones:

Blogs:

http://patshaughnessy.net/  – A ruby guy with very interesting posts on a different topics

https://vasil.ludost.net/blog/ – Very good sysadmin blog (Most of the articles are written in Bulgarian)

http://danielmiessler.com/study/ – Nice articles

http://chzv.net/  – Very good security related articles

https://major.io – DevOP in RackSpace

http://www.xaprb.com – Author of High Performance MySQL, some very nice articles

 

https://nickcraver.com/blog  – This is the blog of Nick Craver  (Sysadmin at StackOverflow

http://www.dedoimedo.com – Very nice linux/software (and not only) articles

https://calomel.org – Very good explained articles with some nice scripts

http://www.ducea.com/ – Blog of Marius Ducea, Freelance Linux Sysadmin – great posts

http://everythingsysadmin.com/  – Thomas A. Limoncelli – (The practice of system and network administration) .. worked for Google, ServerFault , Bell labs …etc

http://thecpaneladmin.com/  – Good cPanel related articles , tips and tricks

https://www.evonide.com/  – Interesting security blog. This guy won 20 ,000$  from PornHub for hacking their website …nice 

http://www.catonmat.net/blog/bash-vi-editing-mode-cheat-sheet/  – Bash vi-like editing mode

 

PostgreSQL

Following a select statement through postgres internals

MySQL

 http://www.palominodb.com/    – This is nice blog having high quality mysql related articles on it

BIND Server Online book

http://zytrax.com/books/dns/

 

Technical Stuff

http://www.eventhelix.com/realtimemantra/#.VFzn8vHCpUQ  – Nice sequence diagrams

http://www.server-world.info – Extremely simple and usefull examples for all kind of server/distro administration

What every programmer should know about memory, Part 1

What every programmer should know about memory, Part 2 – CPU caches

What every programmer should know about memory, Part 3 – Virtual Memory

 

Nice stuff about web for Web Developers:

https://hpbn.co/#toc

 

Tech Blogs Of The Big Guys

https://blog.cloudflare.com/   – Technical blog from CloudFlare, still very nice posts about their infrastracture

Found this nice github list of a different tech blogs.