They do still give out birthday bonus codes. Here's the one i just got a week ago for 200 points.
Drive Off with a Birthday Bonus
of 200 Hertz #1 Awards® Points!
With your birthday coming up next month, it’s a great time to take off and celebrate with a bonus of 200 Hertz #1 Awards Points on upcoming rentals through September 30, 2010. It’s valid on Standard or Leisure Weekend or Weekly Rental rates for Full-Size 4-Door vehicles and above, including Hertz Prestige Collection. Simply use PC# XXXXXX when making your reservations and remember to first add #1 Awards if it isn’t already in your profile. Happy Birthday!