You may also want to check out their first game widget creation, Widget Monkey. With over 12,000 downloads already, it is one of the most popular free widgets available. For those of you who aren't familiar, WidgetMonkey is a 3D Monkey ragdoll which you can make it do crazy things.
Besides that, Widget Monkeys seems to have something up its sleeve. They have announced upcoming shareware versions of their game widgets for $1.99. The shareware versions will include more levels, options, and the WidgetMonkey theme song.
Monkey Marbles requires Mac OS X 10.4 or later to run. For more information on WidgetMonkeys or to download their game widgets, follow the links below.