{assign_variable:master_weblog_name="blog"}
{assign_variable:master_weblog_status="open"}
{exp:rss:feed weblog="{master_weblog_name}" status="{master_weblog_status}"}

<?xml version="1.0" encoding="{encoding}"?>
<rss version="2.0"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:admin="http://webns.net/mvcb/"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <channel>
    <title>{exp:xml_encode}{weblog_name}{/exp:xml_encode}</title>
    <link>{weblog_url}</link>
    <description>{weblog_description}</description>
    <dc:language>{weblog_language}</dc:language>
    <dc:creator>{email}</dc:creator>
    <dc:rights>Copyright {gmt_date format="%Y"}</dc:rights>
    <dc:date>{gmt_date format="%Y-%m-%dT%H:%i:%s%Q"}</dc:date>
    <admin:generatorAgent rdf:resource="http://expressionengine.com/" />
{exp:weblog:entries weblog="{master_weblog_name}" limit="10" rdf="off" dynamic_start="on" disable="member_data|trackbacks" status="{master_weblog_status}"}
    <item>
      <title>{exp:xml_encode}{title}{/exp:xml_encode}</title>
      <link>{title_permalink=site/index}</link>
      <guid isPermaLink="false">{title_permalink=site/index}#When:{gmt_entry_date format="%H:%iZ"}</guid>
      <description>{exp:xml_encode}{summary}{body}{/exp:xml_encode}</description>
      <dc:subject>{exp:xml_encode}{categories backspace="1"}{category_name}, {/categories}{/exp:xml_encode}</dc:subject>
      <dc:date>{gmt_entry_date format="%Y-%m-%dT%H:%i%Q"}</dc:date>
    </item>
{/exp:weblog:entries}
    </channel>
</rss>
{/exp:rss:feed}

{assign_variable:master_weblog_name="default_site"}
{exp:rss:feed weblog="{master_weblog_name}"}

<?xml version="1.0" encoding="{encoding}"?>
<rss version="2.0"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:admin="http://webns.net/mvcb/"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <channel>
    <title>{exp:xml_encode}{weblog_name}{/exp:xml_encode}</title>
    <link>{weblog_url}</link>
    <description>{weblog_description}</description>
    <dc:language>{weblog_language}</dc:language>
    <dc:creator>{email}</dc:creator>
    <dc:rights>Copyright {gmt_date format="%Y"}</dc:rights>
    <dc:date>{gmt_date format="%Y-%m-%dT%H:%i:%s%Q"}</dc:date>
    <admin:generatorAgent rdf:resource="http://expressionengine.com/" />
{exp:weblog:entries weblog="{master_weblog_name}" limit="10" rdf="off" dynamic_start="on" disable="member_data|trackbacks"}
    <item>
      <title>{exp:xml_encode}{title}{/exp:xml_encode}</title>
      <link>{title_permalink=site/index}</link>
      <guid isPermaLink="false">{title_permalink=site/index}#When:{gmt_entry_date format="%H:%iZ"}</guid>
      <description>{exp:xml_encode}{summary}{body}{/exp:xml_encode}</description>
      <dc:subject>{exp:xml_encode}{categories backspace="1"}{category_name}, {/categories}{/exp:xml_encode}</dc:subject>
      <dc:date>{gmt_entry_date format="%Y-%m-%dTH:%i:%s%Q"}</dc:date>
    </item>
{/exp:weblog:entries}
    </channel>
</rss>
{/exp:rss:feed}

{assign_variable:master_weblog_name="default_site"}
{exp:rss:feed weblog="{master_weblog_name}"}

<?xml version="1.0" encoding="{encoding}"?>
<rss version="2.0"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:admin="http://webns.net/mvcb/"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <channel>
    <title>{exp:xml_encode}{weblog_name}{/exp:xml_encode}</title>
    <link>{weblog_url}</link>
    <description>{weblog_description}</description>
    <dc:language>{weblog_language}</dc:language>
    <dc:creator>{email}</dc:creator>
    <dc:rights>Copyright {gmt_date format="%Y"}</dc:rights>
    <dc:date>{gmt_date format="%Y-%m-%d %T %H:%i:%s%Q"}</dc:date>
    <admin:generatorAgent rdf:resource="http://expressionengine.com/" />
{exp:weblog:entries weblog="{master_weblog_name}" limit="10" rdf="off" dynamic_start="on" disable="member_data|trackbacks"}
    <item>
      <title>{exp:xml_encode}{title}{/exp:xml_encode}</title>
      <link>{title_permalink=site/index}</link>
      <guid isPermaLink="false">{title_permalink=site/index}#When:{gmt_entry_date format="%H:%i"}</guid>
      <description>{exp:xml_encode}{summary}{body}{/exp:xml_encode}</description>
      <dc:subject>{exp:xml_encode}{categories backspace="1"}{category_name}, {/categories}{/exp:xml_encode}</dc:subject>
      <dc:date>{gmt_entry_date format="%Y-%m-%d %T %H:%i:%s%Q"}</dc:date>
    </item>
{/exp:weblog:entries}
    </channel>
</rss>
{/exp:rss:feed}

{assign_variable:master_weblog_name="default_site"}
{exp:rss:feed weblog="{master_weblog_name}"}

<?xml version="1.0" encoding="{encoding}"?>
<rss version="2.0"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:admin="http://webns.net/mvcb/"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <channel>
    <title>{exp:xml_encode}{weblog_name}{/exp:xml_encode}</title>
    <link>{weblog_url}</link>
    <description>{weblog_description}</description>
    <dc:language>{weblog_language}</dc:language>
    <dc:creator>{email}</dc:creator>
    <dc:rights>Copyright {gmt_date format="%Y"}</dc:rights>
    <dc:date>{gmt_date format="%Y-%m-%d %T %H:%i:%s%Q"}</dc:date>
    <admin:generatorAgent rdf:resource="http://expressionengine.com/" />
{exp:weblog:entries weblog="{master_weblog_name}" limit="10" rdf="off" dynamic_start="on" disable="member_data|trackbacks"}
    <item>
      <title>{exp:xml_encode}{title}{/exp:xml_encode}</title>
      <link>{title_permalink=site/index}</link>
      <guid isPermaLink="false">{title_permalink=site/index}#When:{gmt_entry_date format="%H:%i"}</guid>      <description>{exp:xml_encode}{summary}{body}{/exp:xml_encode}</description>
      <dc:subject>{exp:xml_encode}{categories backspace="1"}{category_name}, {/categories}{/exp:xml_encode}</dc:subject>
      <dc:date>{gmt_entry_date format="%Y-%m-%d %T %H:%i:%s%Q"}</dc:date>
    </item>
{/exp:weblog:entries}
    </channel>
</rss>
{/exp:rss:feed}

http://23rdworld.com/2009/12/23/how-to-fix-your-expressionengine-rss-template/

This template removes seconds from date fields used in the <item> which cause multi-posting (on each edit) of entries. These are the minimal fixes to the current default EE RSS Template, I've also uploaded an [improved template](http://snipplr.com/view/25354/ee-rss-template-improved/ ) as well. For more information see my blog post (url above)

EE Default RSS Template (Fixed)

template

XML