Resources:
teh_indy resource post
Nadine imagination
icons_with_love
cyberelf

Brush credits:
teh_indy
elli
sinecure
dtissagirl
crumblingwalls
daughterofsnape
oxoniensis
inexorablyhere
onfireicons
v-brush
Miss M
Ancient Secret
Rust 'n Grunge
Tech brushes
Paper
Hybrid Genesis

Screencaps:
_jems_
Secret Obsession

Textures:
Of the Sky
Blimey textures

Tutorials:
Icon text

Stock images:
Getty Images
Stock Xchange

I'll try to keep this up to date, but I can't promise