I want to use tags in my computer for my email, my files, my calendar items, my contacts...

I have always thought it was odd that I had to have different category lists everywhere in my computer and then had to keep them aligned. Will somebody please implement global tags that I can see on my computer so that I can look at all of the calendar items, contacts, tasks, emails, and files that have those tags?

Funny how new paradigms (like web 2.0) bleed into the old spaces.