There's much talk of the GTD plug-in, and FC PlanPlus - when the GTD plug-in arrives we can all review it's qualities - for now, I need my e-mail organized better than Outlook does on it's own (I have about 300 folders and 50 rules, so it's not for a want of trying that it frustrated me).
I've found the NEO tool from Caelo to be very helpful in this regard - it has radically improved my 140+ message per day inflow. As it appears not to have been mentioned here, I thought I'd point others to it.
It is basically a comprehensive index for Outlook, which automatically files all messages by time, contact, etc. regardless of their location within the Outlook folders. For someone like me, that means no 'lost' messages because they got filtered and I didn't notice. It also means you can see every correspondence to and from an individual (regardless of how many e-mail addresses they have) as well as everything they were 'copied' in on. All of this greatly improves productivity.
But the best thing about it, is the tray icon - which reports the sender of each e-mail, as it arrives. So without even opening the inbox, you can chose to ignore the message until later - now wiht heavy inflow of both important and less so (at best), this is a real time saver.
If you're interested take a look http://www.caelo.com/a/rl.php3?i=4G0TV
(that's an affiliate address by the way, I get credited for your visit if you buy - if you really think I should not then simply go directly there www.caelo.com).