Hi Reena,
As you said you send cards for occasions,you can try out yahoo greentings.com .create a log in for you and add all the contacts you have with their respective date of birth details. You can also try american greetings.com , both these r the ones i use.they keep sending reminders atleast one week in advance and keep reminding u with e mails quiet often. U can also choose to send e cards for free from these sites.
Regards,
Hari