I've been using David Allen's Getting Things Done method (GTD) to organize my time for over a year now. I have a fairly typical set of "@" folders in my Outlook mailbox, such as:
@Action - things to be done as soon as possible, but not on a specific day
@Reading <listname> - things to read when I have time (several of these, one for each mailing list I'm on)
@Someday - ideas for Someday/Maybe
@Waiting - things on hold while I'm waiting for a response from someone
I also have many folders with no "@" on them, which are my project support materials and reference. When I'm assigned a task, I create a folder for its correspondence. But I was having trouble with emails that didn't fall into any assigned task -- typically things that I've been copied on but have no immediate action. However, I want to keep a closer eye on them than burying them among my reference folders, because they may turn into an assignment quickly.
So I added the folder @Watching. I create a subfolder for each topic, and track the email traffic to these subfolders as it arrives. Now, by expanding @Watching, I see a list of topics I'm tracking. If nothing happens or the task is assigned to someone else, I can delete the folder and its contents easily. If the task is assigned to me, I can just drag it up out of @Watching so that it becomes a regular reference folder.
So far, I'm liking this refinement. But of course, I will keep evaluating it as I go.