National Car Rental is offering free (normally $50) Emerald Club membership, plus 1000 bonus miles on your first rental, and 500 per rental for each additional rental until June 25th. Even if you are a current EC member, you can still sign on for the promotion to get the miles.
Emerald Club + Many Miles
Rent with National® from March 20 through June 25, 2006. You’ll earn 1,000 frequent flyer bonus miles with your first rental, and 500 bonus miles on each additional rental during the promotion period. Bonus miles will be credited to your frequent flyer account 6–8 weeks after the promotion ends.