ArtRage is a free painting program.
No layers, no effects, limited tools, designed to simulate "playing with
paint without the mess".
http://www.ambientdesign.com/artrage.html

Wink captures screenshots or images which allows you to create tutorials
or add annotates.
http://www.debugmode.com/wink/

Unusual images of the micro world.
http://www.microscopy-uk.org.uk/micropolitan/index.html

The flexible freeware panorama software from WPanorama with a selection of panoramic images.
http://www.wpanorama.com/wpanorama.php

NASA's Mars Rover website, home to 3D, panormaic, and other photos from Mars http://marsrovers.jpl.nasa.gov/home/index.html

Digit Magazine with Canvas 7 details here.
http://www.digitmag.co.uk/canvas7/

The Arachnophilia Web Editor careware.
http://www.arachnoid.com/careware/