Mymemorizer is a free web calendar service that allows users to create & maintain online appointments, tasks and events such as birthdays, wedding days, parties or meetings and get free reminders vis SMS text message, Email2SMS or regular EMail.

Key features include:

-Add events for important dates or subscribe to shared groups.
-Get reminder on your mobile device through SMS text message or email

While free SMS reminders are limited to 2 per day, you can buy credits or specifiy your Email2SMS email address such as +mobilenumber@carrier.com to get alerts dierctly to your mobile device.

Also read a review of Kiko which offers free calendar alerts & reminders through SMS text messages.