You can move a message to Tasks or Calendar folder to create a new item one of three ways:

1. Drag and drop on the folder. (In Outlook 2003, drop on the buttons at the bottom of the Navigation Pane.) This adds the message body to the note field of the new item.
2. Right click, drag and drop to a folder. Use this method to control how the message is attached to the item - Copy as Text, as Shortcut, as Attachment or Move as Attachment.
3. Select the item and choose Edit, Move (or Copy) to Folder... and select the folder from the folder picker dialog. This adds the message body in the Notes field.

Fill in the remaining fields and set reminders, then Save.

Need a task but only want part of the message included? Copy it, and then paste on an empty space in the Task folder - a new task opens with the copied text in the note field. (Like the methods above, it works on all Outlook items types.)