CovertClick is a tool for masking the http referer in a link so the website being navigated to is unable to track where the link originated. To use it, simply add http://www.covertclick.com/ to the beginning of any link that you don't want to have the referer sent. It also properly handles complex urls that contain query strings or anchors. CovertClick is a free service. No intermediate page with ads ever appear. Instead, the redirect is instant.

You can learn more about it at the CovertClick website.