Here is a small selection of links to frequently visited sites. Let me know if a link is broken or you know a nice addition for these lists.
ELECTRONICS
tronixstuff.com
Fun and learning with electronics
The Art of Electronics
The Art of Electronics 3rd Edition
SparkFun Electronics
Online retail store with blog and tutorials
Parallella Computing
Supercomputing for Everyone
OpenCores
Open source hardware IP-cores
New Horizons Zynq Blog
Zynq Design From Scratch
Hackaday
Fresh hacks every day
Elektor Projects
Sharing electronics projects
EEVblog
Electronics engineering video blog
EDA Playground
EDA Playground
Dangerous Prototypes
A new open source hardware project every month
Circuit Cellar
The World's Source for Embedded Electronics Engineering Information