Boards

Arduino
Seeed Studio
Modern Device
Adafruit
SparkFun
Liquidware
Beagle Board
Gumstix
Illuminato X Machina
Bug Labs

Parts and Components

Jameco
DigiKey
Mouser
dipmicro electronics
Farnell
Newark
All Electronics
BG Micro
Ax-Man Surplus (my favorite local place)

Software

Processing
AVR Libc
Android Open Accessory Development Kit

Learn to Build Things

Hack A Day
Make Blog
EEWeb
Instructables
AVR Freaks
Electrical Engineering @ StackExchange
element14

Connect with Actual Humans

Ignite
Maker Faire
Dorkbot
NYC Resistor
BarCamp
Twin Cities Maker

Get Inspired

TED
Design and the Elastic Mind
Talk to Me