I've always been a fan of applications that let you spiff up the Windows GUI - that's why I was surprised to learn about Konfabulator - a cool GUI enhancer produced by a company that was recently purchased by Yahoo!.

I installed Konfabulator on one of my machines and it's a pretty neat Widget platform. There are hundreds of quality Widgets available and the core-application is now free thanks to Yahoo! It's a bit of a memory hog (a common complaint with applications like this) but it's well designed and fairly robust. Worth a look if you feel like spiffing up your GUI. Konfabulator is available for both the Windows and MAC operating systems.

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Reviews
ars technica Review of 2.0
Aqua XP Review of 1.8 - 2.0 is the current version