2,500 Delta Skymiles Birthday Bonus
Yep, Delta will give you 2,500 miles just for being born in the month of January (and for buying a ticket and flying by Feb 28, 2011). This offer is technically targeted, but as long as your birthday is in your Delta profile, you should be eligible. They'll even throw in a $100 Delta Vacations gift certificate. This promotion has been happening every month, so if your birthday is in February, don't fret.
This promo actually used to be much more lucrative- with people getting double miles, including MQMs on flights. Delta has since scaled it back, but free miles are free miles so I won't complain. I'll only complain if they stop running this promotion before March!