In general, I don't have a lot of use for the default portlets on the right of the pages (calendar & news), so I like to hide the entire column (slot) and use the space for content. The way to do this in plone3 is to edit the "/portal_skins/plone_templates/main_template" file to remove the "right slot", also known as the "column_two_slot" or "right column":

1. Login to your plone site as the admin.
   
2. Click on "Site Setup" in the upper right hand corner
3. Click on "Zope Management Interface" under the "Plone Configuration" heading
4. Click on the "portal_skins" item
5. Click on the "custom" item
6. Click on the "plone_templates" item
7. Click on the "main_template" item
8. Click the "Customize" button
9. Block-comment via xml style comments the relevant lines by changing this
   

   <tal:comment replace="nothing"> Start of right column </tal:comment>
   <td id="portal-column-two
       metal:define-slot="column_two_slot"
       tal:condition="sr">
     <div class="visualPadding">
       <metal:portlets define-slot="portlets_two_slot">
         <tal:block replace="structure provider:plone.rightcolumn" />
       </metal:portlets>
       &nbsp;
     </div>
   </td>
   <tal:comment replace="nothing"> End of the right column </tal:comment>

   to this:
   

   <!--
      <tal:comment replace="nothing"> Start of right column </tal:comment>
      <td id="portal-column-two"
          metal:define-slot="column_two_slot"
          tal:condition="sr">
        <div class="visualPadding">
          <metal:portlets define-slot="portlets_two_slot">
            <tal:block replace="structure provider:plone.rightcolumn" />
          </metal:portlets>
          &nbsp;
        </div>
      </td>
      <tal:comment replace="nothing"> End of the right column </tal:comment>
   -->

10. The changes should show once the page is reloaded. Of course it may be necessary to clear the browser cache.

Note that the modified "main_template" will now be used (hence the disappearance of the right column) and will now be accessible at the folder "/portal_skins/custom/main_template". The unmodified "main_template" will still be at "/portal_skins/plone_templates/main_template" so be careful which one you modify if you make further customizations.