I myself use Outlook 2007, labels and a folder called “@Archive”. All the mails in my inbox that I have read, I label (and if action required, add the follow up flag as well) and move them to the @Archive folder. Therefore my inbox only holds my unread emails.
This has 2 advantages. First, if I get an email from customer X about product Y, I can add two labels (or have rules do it). With search folders, don’t need to think if I should add the mail to the client folder or to the product folder, I now can always find it either way.
Mails from mailing lists go straight to the @Archive but leave them unread. I can the “Unread Mail” search folder to quickly find them as well, and they don’t clog up my inbox. (They have their own label as well, so could search on that if needed)
Alexander