Automated Mailer in Rails ?

I've setup my rails app to send mail, say when someone registers they
get a 'hey thanks for registering' email; that works fine.

That's firing thru using sendmail ok.

Next up I've got a facility for people to set reminders, say for
birthdays.

So to remind these people I'd like something to run maybe daily and when
it sees someone's birthday is coming up fire off an email to remind
them.

Any ideas how I could do this automated mailing in Rails?

cron and script/runner

-philip