This has a really nice slide in effect, but also a really nice built in content scrollbar. I've been using it as a Dashboard widget palette, looks really nice and it's operation is pretty smooth.
These are all sub-$10, that said there's a whole lot more completely free code kicking around, and while some is of very questionable quality, there are some other Widgets that are as good or better than the commercial options. I'm using something called Gridster for my Dashboard, unfortunately it looks like the sponsoring company has been bought, but what's there now is still very good. It supports drag and drop re-ordering, widget resize, dynamically add and remove widgets, has load / save facilities etc etc ...
Last but not least, a Widget I've been playing with off and on for quite some time is jsPanels. Now jsPanels is a hugely underrated / largely unknown project designed to allow "windows" style panels to be utilised inside web based applications. I spent a little time last year working with the author to enhance some of the features available and it's an incredibly powerful bit of code, so watch this space for more in the future. Currently I'm using it for displaying online users, but there's far more to come.