Avoiding forgotten email attachments

How many times do I forget to attach a file to an email? Probably at least once a week. Always embarrassing, and usually when I am trying to project a professional impression. PC World has some helpful tips to avoid the problem, at least with Microsoft Outlook. It suggests several free tools that scan your outbound messages for keywords like "file," "attached," and "attachment." If they detect such a word but there's nothing attached, you get an alert - allowing you to attach the intended file and avoid future embarrassment.
Outlook 2007 users can grab the Missing Attachment PowerToy, or the more robust Forgotten Attachment Detector (which supports custom keywords and can even warn you about blank subject lines). If you're using an earlier version of Outlook, try Attached4Sure which supports all versions dating back to 2002.
I don't know of any similar tool for Outlook Express, but Google Mail users get the same service with its Forgotten Attachment Detector, with is a setting within the program.