AOL Rings Up New Shopping Service  NEW YORK (Reuters) - America Online, the world's largest  Internet service provider on Monday launched an overhauled  online shopping center it hopes will help it keep pace with  competitive offerings by Yahoo Inc.&lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=YHOO.O qtype=sym infotype=info qcat=news"&gt;YHOO.O&lt;/A&gt;, Google Inc.  &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=GOOG.O qtype=sym infotype=info qcat=news"&gt;GOOG.O&lt;/A&gt; and Shopping.com, executives said.