You can crop an image in Word, Excel, PowerPoint, or Outlook 2010 using shapes such as a square, triangle, etc. Note that in Outlook this will need to be done in a message window.
1. On the “Insert” tab, click “Picture” to insert an image from your computer.
2. On the “Format” tab, click “Crop” button, pass your mouse over “Crop to Shape,” then select any shape you like, which will be applied on your picture.
These instructions, along with illustrations of this, can also be found in SharePoint > Software Users Group > Shared Documents > Cropping an Image to a Shape.