Thrifty and Dollar are the same company. Just make sure you bring your insurance documentation when dealing with them at the airport, otherwise easy sailing with them.
My only experience with Budget was in San Francisco, and it was a less than good one... so I don't recommend them. Not to mention, their cheapest offering is close to $100 more than what I previously posted
on a different note... I've done this in some cities. Toyota Rent a Car. You rent a car from a Toyota dealership... usually a Corolla for $20-30/day (or other models for other prices). I've had nothing but good experiences with them, and they're usually cheaper than the normal agencies.
To add to what I've previously posted, back to rate searches. These are the CHEAPEST cars they offer
Alamo is $266.89
National is $271.69
Eagle (local company at MCO) is $272.92
EZ (another local company at MCO) is $282.69
Avis is $288.87
L&M is $323.94
Enterprise is $329.56
Dollar is $330.53
what else... a good Car Rental website is
http://www.carrentalexpress.com They search local companies in the cities and turn up prices and options