From pda4x comes E-mail Triage, an extension to Outlook, both for Windows Mobile 5 and 6, which will help you transform an e-mail into either a Calendar appointment, Task or even both.

Download the appropriate cab file for your Operating System and install, without the need of a Soft Reset. After that, your e-mail view soft menu will get richer by the two newly available commands, “Move to Tasks” and “Move to Calendar”. The extension will create a new Calendar event or Task with the same title as your e-mail which generated it, having the e-mail’s text as a description. You can then edit proper date and time of the occurence by editing the entry.

Thanks for the tip, Michael!