Here is great article that talks about how great copy can dramatically improve your conversion. http://www.grokdotcom.com/2009/07/13/can-copy-create-added-value-on-its-own/
My collection of links to help with conversions:

http://videos.webpronews.com/2009/04/13/making-your-ecommerce-site-convert/

UserTesting.com – This is a fast and cheap way to get feedback on your site. $29.