Dan already posted how to get free wifi on A"A using the promo code AAWiFi76194A1
Now you can get free wifi on Airtran flights also by using the code 159FLT3161
Both expire August 31st of 2009.
You need to create an account, log in, click buy (for the cheapest package), and then enter the promo code and click Update Total.
No credit card needed, and you don't even need to give a real e-mail address. They don't send a confirmation e-mail.
Enjoy!