After hearing about Google's new GMail product, where email is "categorized" instead of just jammed into folders, I was thinking it would be neat if you could do the same thing with files in the Windows file system. 

Basically, you'd need a way to index the existing files, categorizing them according to the user's needs.  For example, one Word document may be categorized in the 'Word documents', 'Code fragments', 'Memos', and 'Development Team' categories...instead of just getting filed away in 'My Documents' under, at best, a folder representing one of those categories. 

The beauty of this would be in searching.  Besides the usual 'search by name' junk, you could restrict a search to certain categories.  (think...“I know I sent that code fragment in a memo to the whole development team“)

Using Google, I looked around for such a thing and found that Microsoft's Longhorn is packaged with exactly what I'm dreaming about: they call it WinFS and the article that dashed my dreams of fame and fortune is here.