♠ resource post.
I use Photoshop CS2 to make my icons.

Non-Screencap Images:
Jensen Ackles
Jensen Ackles
Shawn Ashmore
Steve Bacic
Katie Cassidy
Selena Gomez
Mariska Hargitay
Charlie Hunnam
Famke Janssen
Anna Paquin
Ryan Reynolds
Ryan Reynolds
Rodrigo Santoro
Aaron Stanford

ARKive (wildlife photos)
Asian Fanatics
Last FM
SXC
Vista Wallpapers
Young Teen Idols

Screencaps:
Striped Wall
Irish

Scans:
I used to use scans by a user named "Matsuchan3" on Photobucket, but am no longer able to find her album.
aalenchan @ lj
jrock_scans @ lj

Brushes, Textures, Etc.:
skeletton @ lj
zinzibar @ lj

Never forget that Google Images can turn up good shots too.

If I have used something of yours and failed to credit it, PLEASE do not hesitate to leave a comment here and tell me.