As a workplace Windows user, I'm always on the look out for good ways to bring in the OS X experience. There have been some interesting Web sites that attempt to rebuild OS X in a browser window, but none of them are terribly satisfying beyond novelty.
There is a new site up that has great potential, though it currently doesn't feel enough like OS X. It's called Widgetop, and it is a stand-in for OS X Tiger's Dashboard in a window. It runs most of the widgets that are staples of the OS, but it feels a little bit weird for the time-being, and the interface is decidedly Windows XP. It is quite cool that it literally runs Apple widgets, though. That's service.
What are your Macintosh usability oases when you're stuck with Windows?
