Disable Magento modules not used (check if you really don't use any of them), place this file in app/etc/modules/, also disables the logging of visits (can break product compare)

Z_Disables.xml

<?xml version="1.0" ?>
<config>
	<modules>
		<Find_Feed>
			<active>false</active>
		</Find_Feed>
		<Phoenix_Moneybookers>
			<active>false</active>
		</Phoenix_Moneybookers>
                <Mage_XmlConnect>
                         <active>false</active>
                </Mage_XmlConnect>
                <Mage_GoogleCheckout>
                	<active>false</active>
                </Mage_GoogleCheckout>
                <Mage_Usa>
                	<active>false</active>
                </Mage_Usa>
                <Mage_Authorizenet>
                	<active>false</active>
                </Mage_Authorizenet>
                <Mage_Backup>
                	<active>false</active>
                </Mage_Backup>
                <Mage_Centinel>
                	<active>false</active>
                </Mage_Centinel>
                <Mage_Compiler>
                	<active>false</active>
                </Mage_Compiler>
                <Mage_Giftmessage>
                	<active>false</active>
                </Mage_Giftmessage>
                <Mage_PaypalUk>
                	<active>false</active>
                </Mage_PaypalUk>
                <Mage_Persistant>
                	<active>false</active>
                </Mage_Persistant>
                <Mage_Weee>
	                <active>false</active>
	        </Mage_Weee>
		<Mage_Productalert>
			<active>false</active>
		</Mage_Productalert>
		<Mage_Tag>
			<active>false</active>
		</Mage_Tag>
	</modules>
	<!-- Disable visitor logging -->
	<frontend>
	        <events>
        	    <controller_action_predispatch>
                	<observers><log><type>disabled</type></log></observers>
	            </controller_action_predispatch>
        	    <controller_action_postdispatch>
                	<observers><log><type>disabled</type></log></observers>
	            </controller_action_postdispatch>
        	    <customer_login>
                	<observers><log><type>disabled</type></log></observers>
	            </customer_login>
        	    <customer_logout>
                	<observers><log><type>disabled</type></log></observers>
	            </customer_logout>
        	    <sales_quote_save_after>
                	<observers><log><type>disabled</type></log></observers>
	            </sales_quote_save_after>
        	    <checkout_quote_destroy>
                	<observers><log><type>disabled</type></log></observers>
	            </checkout_quote_destroy>
        	</events>
    </frontend>
</config>