The Parking Spot comes to mind, but it's hard for me to fathom any traveller who would use airport parking in locations other than where they live with any great regularity (I did this once when it was cheaper to park my rental car overnight than to book two seperate rentals, but it was an exceptional circumstance).

I think parking threads are best served in the regional forums and not a consolidated one for all of the US, let alone other countries.