Apple has partially opened their Dashboard Widgets page in their Mac OS X Downloads Area.
At present the Download Page is only partially active with file names linking to missing pages, but download links for many of the widgets are presently available.
3rd party widgets include a mini RSS reader, solitaire, Send SMS, Quicktime player, FedEx tracker and more... Widgets are activated by simply double clicking on their icon in Mac OS X 10.4's Finder.