I have had my eye on the Pet Flys carriers for awhile...I fly at least 4-5 times per year with one or more of my dogs so it might make the price tag a little easier to swallow.
In the car, I have a carseat that I sometimes buckle them into (should be better about this but I'm just not great at it yet).
I have my sherpa sport sack for when I need to be incognito with my chi: Sherpa Sport Sack Pet Carrier Dog Products - GregRobert
I really want one of the plush carriers Ivy's Mom makes on the forum.
For flying I also have used the Bergan Comfort Carriers. We had an AKC sherpa airline approved carrier but man was it ugly.