Screen Mates

Desktop Animation
Free Screen Mates characters and animals, for Windows 2000, XP and Vista.
http://www.desktopanimation.net/

DesktopMates
Animated characters as interactive companions, capable of speech and doing tasks, using Microsoft Agent Technology.
http://desktopmates.com/

eSheep 2
An animated sheep interacts on the desktop, including sticky note reminders and email notification.
http://www.geocities.com/siennaj/Esheep2/

Global Beach Limited Virtual Creatures
A tarantula and a MOPy fish, that can live on a PC as long as it is cared for and nurtured is offered. A free, limited run version is available.
http://www.virtualcreatures.com/

Global Pets 2002
A virtual pet simulation that includes an online community.
http://www.mezaman.com/globalpets/home.asp

Happy House - Your Virtual Rodent
A hamster that will walk around, stuff its cheeks with food, unload the food, eat, sleep, groom itself and sleep. For Windows and Mac.
http://www.maniform.com/stuff/hamster.htm

inDesktop
Free, interactive, animated programs including television and movie themes.
http://www.screenmates.com/

Oska DeskMates
Interactive characters for Windows that react when touched, and can be moved around the screen with the mouse.
http://www.oska.com/

TopDesktop
Screen Mates in the categories of animals, cartoons, holidays, people and sports.
http://www.topdesktop.com/mate1.htm

Widgipedia
A Widgets resource that includes a gallery, samples, tutorials, and community.
http://www.widgipedia.com/

XPenguins
Animated penguins run around the desktop and jump off open windows. WinPenguins or the Linux/Unix version available. Free, licensed under the GNU GPL.
http://xpenguins.seul.org/