Some interesting desktop innovations in Microsoft's Longhorn Alpha Preview 3 (the new Windows): Libraries, pivot views, Carousel view and stacks.
Libraries. "In this build, special shell folders have been replaced, sort of, by a new construct called a library. A library is a virtual folder that intelligently gathers information about files on your system and presents them to the users in a collection. [...] Note that libraries don't actually contain anything physically; instead, they are a special collection of shortcuts, similar to the Control Panel in XP. The files themselves could be anywhere on your system, though most libraries are limited to searching particular folders for performance reasons. As I understand it, the objective here is to transparently shield the user from having to worry about physical disk locations, and it seems like a good idea. [...] Longhorn includes the Document Library, Game Library, Music Library, My Contacts, and Picture & Video Library. [...] The Document Library will logically replace My Documents and is, naturally, a collection of all of the documents on your system. By default, the Document Library collects documents from My Documents, the desktop, and Shared Documents. It does not collect pictures, videos, or images."
Pivot views. "In Longhorn, libraries can be filtered to display only certain types of content. When dealing with libraries, a filter (or view) is called a pivot. So, for example, you might display all pictures and videos in the Picture & Video Library, but you might want to filter the view by various criteria as well (size, date, whatever); this view of the data is a pivot. You can also modify the default view, or pivot, for each library and determine which physical folders it links to."
Carousel view. "The My Contacts Library features a new Explorer view style called Carousel. [...] Graphically, an icon representing your user sits at the center of the carousel, and lines, or spokes, branch out from the center towards your contacts. In Carousel view, items can be grouped by various criteria, such as relationships. In the relationships concept, you might have people sorted by family, friends, work, and the like. So you'd see lines radiating out from your icon toward these groups. Items that are logically further away from you (alphabetically, those items that are further from the letter A) will graphically fade as they move further from the center of the carousel (you)."
Stacks. "In My Contacts, you can arrange contacts by Name, Email, Work Email, Personal Email, Home Phone, Work Phone, or Online Status, but you can also utilizing a new feature called Stacks. Because you can't actually work with stacks in 4015, it's unclear what the feature does, but you can stack contacts by the same list of criteria by which you can arrange them, and you can also unstack them. Stacking and unstacking might be related to the Carousel view but, again, that's unclear right now."
(Enormous quantities of text copy-and-pasted above because I'm never very optimistic about OS preview commentary staying on the www for long.)