Class tools: Clip art

ClipartCastle
Over 1,000 cliparts ready to be downloaded (free or nominal fee)

Freestockphotos.com
Free photos for personal or commercial use.

Freegraphics
Excellent source of cliparts, wallpaper, screensavers, and much more.

Microsof't's clip art and media
Over 500 hundred clip art and media that can be downloaded free of charge. Categories from academic to web elements.

SXU.hu
Stock exchange have over 100,000 photos free of charge for educators.