My favorite is Parking Spot 2 on Desert Dr (off Camp Creek pkwy), we use the covered parking. Also check if your employer gets a discount with them, with mine we get 40% off. About a 10 minute shuttle ride from airport, they pick you up and dropoff in front of your car, and you get free bottles of water when you checkout.

Not necessarily the lowest $$$s, but provide good shuttle service, hopefully covered parking, etc.

Using Way.com found some dirt cheap options, but reviews are not good.