Birthday Alarm. com apparently will let you set up a point where friends can put in their birthday's so you can contact them. Feel free to try this out (Birth years are optional).
Here's the auto generated e-mail I's supposed to use to spam my friends.:
I would like to be reminded of your birthday each year using an excellent service offered by BirthdayAlarm.com.
Please click on the following link for me and enter your name and birthday, it only takes a few seconds: