How do I create a menu shortcut which involves the delete key?
You can edit the property list that stores the shortcuts directly. For example open ~/Library/Preferences/com.apple.AddressBook.plist with TextMate or TextWrangler, and add:

&lt;key&gt;NSUserKeyEquivalents&lt;/key&gt;
&lt;dict&gt;
    &lt;key&gt;Delete Card&lt;/key&gt;
    &lt;string&gt;~@&amp;#x0008;&lt;/string&gt;
&lt;/dict&gt;


The shortcut strings are documented in http://www.hcs.harvard.edu/~jrus/Site/Cocoa%20Text%20System.html.