Third column for the default template

[SecondShoe +]

Open layout.tpl .

Find:

<!-- // Content // -->
						<br /><br />
						{* This includes the content portion *}
						{include file=$body}
						<!-- // End Content // -->
					</div>
				</td>

Add after on a new blank line:

<td valign="top" width="200">
					<!-- // Right Side -->
						<div id="sidebar">
							<h1>{$smarty.const.LANG_MEMBER_NAVIGATION}</h1>
							<div class="left-box">
								<ul class="sidemenu">
									{if $smarty.session.username<>'' || $smarty.cookies.username<>""}
										<li><a href="{$smarty.const.URL}/userindex.php">{$smarty.const.LANG_MY_ACCOUNT}</a></li>
										<li><a href="{$smarty.const.URLS}/usercheckout.php">{$smarty.const.LANG_TPL_PLACE_AD}</a></li>
										{if $canSaveFavorites=="Y"}
										<li><a href="{$smarty.const.URLS}/userfavorites.php">{$smarty.const.LANG_TPL_VIEW_FAVORITES}</a></li>
										{/if}
										<li><a href="{$smarty.const.URLS}/userbrowselistings.php">{$smarty.const.LANG_TPL_MODIFY_AD}</a></li>
										<li><a href="{$smarty.const.URLS}/logout.php">{$smarty.const.LANG_TPL_LOGOUT}</a></li>
									{else}
										<li><a href="{$smarty.const.URLS}/login.php">{$smarty.const.LANG_TPL_LOGIN}</a></li>
										<li><a href="{$smarty.const.URLS}/usercheckout.php">{$smarty.const.LANG_TPL_PLACE_AD}</a></li>
									{/if}
								</ul>	
							</div>
						</div>
					<!-- // End Right Side -->
</td>

Modify it according to your needs.