Organize Your Outlook E-mail with ClearContext Personal
This is one of those things that's better demonstrated than explained, so I'm going to let the promo video up top do the heavy lifting. It's worth watching, because it's not immediately clear how to start using ClearContext after you install it.
In fact, at first I didn't think it was working, but it turns out the software doesn't currently support IMAP -- and I use an IMAP-powered Gmail account in Outlook. ClearContext also has difficulty working alongside Xobni, my all-time favorite Outlook add-in, so I don't know if this is a keeper for me.
That said, I know ClearContext has tons of fans, so it's worth a try if you're an organization-strapped Outlook user. ClearContext Personal is free; it works with Outlook 2003 and 2007.