We're working on a very interesting task of replacing default SharePoint document library UI with a new Silverlight-based UI mimicking Windows Explorer to some extent but providing SharePoint-specific functionality. It integrates with MOSS or WSS via web part and displays contents of any folder you might have in a data grid and shows selected document's properties and preview (streaming video or pictures) on the bottom (there will be other layouts later as well). It also supports full-screen browsing of your SharePoint repositories, allows real-time change refreshes and enables basic operations on the document via context menu.  This is not part of SharePoint team's efforts and will not be part of SharePoint "14", but will be available to the public along with full source code sometime later this calendar quarter.