LinkBlip is a site where you can monitor when someone has clicked a link you sent them. Have you ever sent someone an email and never heard back? If you send them a LinkBlip URL, you'll automatically be notified by email when they click on it. This site also tells you what city and state they were in when the clicked the link.
How it works:
# You enter a URL and your email address into the above form.
# It generates a special URL for you, which you can then email to someone.
# When someone clicks that special URL, you are notified by email with the time they clicked it as well as the city and state they were in. The recipient of the URL never knows the difference.
Website: http://linkblip.com/