Well, this doesn't really qualify as "cool", but I found it helpful...
Because of the nature of my work andthe limited amount of space we're allowed for our email, I found it necessary to save my emails to a network drive. So I wrote a macro that saves all of my emails to a secure drive that only I have access to.
As the macro runs, it saves each email by sender's name and date. Each user gets their own folder usingtheir name. Each folder below the users name is identified by the month/year I got the email. In addition to saving the email, it also saves any attachment that came with the email. Both email and attachements are appended with a date time stamp that corresponds to the date and time that the email was sent. So if someone walks up to me and says "Bob sent you an email in July that said...", I am able to find any email Bob sent me in July. Or any attachment.
There is a downside...
IT hates my macro. The first time I ran it I saved about 3 GB of emails and attachments to my personal drive. When they surveyed disk usage, I got a nice little email asking me to remove the excess junk from my drive.
But there's also an upside...
I told them I would delete my emails if they could guarantee me that they could find any email (or email thread) I ask for. They said yes the could. I asked them if they were willing to take responsibility for anything that I could not find and that they had lost. (This is critical with the work I do.) They said they would.
We now have this little email chat on about an annual basis. And IT has done a wonderful job of living up to their word so far.