Here are some science-themed icons and wallpaper spruce up your otherwise un-sciencey desktop! Enjoy!

Icons
Mac OS X
Great Minds (via Interface LIFT)
Modern Scientists (via InterFace LIFT)
Roboticons (via Mastifnet)
Bees (via Britta/arts)
Organs (by Chistophe Bouchard) (OS X, Windows)
Molecules (by Mark Magnuson)
Arthropods (by Max Fiedler)
Windows
Science Icons by ~MrMunkily (via DeviantArt)
Chemistry Icons by eponas-deeway (via DeviantArt)
Science Icons (via My Biotech Life)

Wallpaper
European Space Agency Wallpaper
NASA HubbleSite
NSF Chemistry & Materials
New Scientist
Materials Research Society
BBC Science & Nature
BBC Planet Earth