Windows only: Microsoft Outlook plug-in Forgotten Attachment Detector analyses your email for clues that you really meant to attach the cover sheet for that TPS report.
The plugin works similarly to most of the other attachment reminders that we've written about before—the difference is that this one is created by Microsoft's Office Labs and only works for Vista and Outlook 2007. Once you try to send a message, if the plugin detects that you meant to attach a file, it will prompt you before allowing you to send the email—and as a nice touch, it will even tell you what triggered the message.
Forgotten Attachment Detector is a free download for Windows Vista, requires Outlook 2007. For a similar utility, check out the Missing Attachment Powertoy—or learn how to create a macro to stop forgetting the subject line.