Quick Parts is a new feature available under Office 2007 as a counterpart to the AutoText feature for the previous versions. It allows you to make a recursive use of the words/text/phrases that are rebundantly used within your emails.
Here's how you can create a Quick Part to hold boilerplate text for insertion in an email message.
Open a new Untitled message.
Write the text you want to reuse.
Select the text, click on the Insert tab> Quick Parts > Save Selection to Quick Part Gallery"
In the "Create New Building Block" window, enter a name for the Quickpart.
Click OK to save it.
To apply the Quick part simply click on the Insert tab>Quick Parts > and make your selection.