The best site I've found for parking discounts to date has been
http://www.longtermparking.com
They have coupons and discounts grouped by state and airport.
At IAH, I use AMPCO Parking.
1) Parking is $10/day for covered parking (a must for Houston) but there is a coupon available from longtermparking.com for a FREE day after a 3day minimum stay. For example, parking from Friday Afternoon to Sunday night only costs $20 instead of $30+tax
2) For every 15 days worth of paid parking, you receive 2 days free. Not much compared to other places I've parked, but its a nice perk.
3) For every Frequent parker card you fill up (15 days), you are supposed to receive 200 Continental Onepass miles. Its been hit or miss on receiving these miles but its a nice surprise to see when you log in every so often.
In Dallas (DFW) I was always a big fan of PCA Parking. The coupons you can get off of longtermparking.com lowered the $10/day daily rate for indoor parking down to $6.50. 30 days worth of paid parking nets you 10 days free. A great deal but since I don't live in Dallas anymore its kinda useless for me.
FWIW, I've heard good things about Wallypark.
They aren't at any airports I fly out of yet (Seattle and LAX only) but the WallyGuard protective walls between cars would be worth my money anyday. I don't know why more parking places don't have this feature. Hell, I'd pay more money to know that some slack-jawed yokel in his SUV isn't flinging his door into my car.
It's kinda scary to think there are some months where my Audi is parked at the airport more often than in my garage. sigh.
[This message has been edited by gunn (edited 10-17-2003).]