Sleepypod Air

Price: $149
More Info: store.sleepypod.com

This Rolls Royce of pet carriers meets major airline carry-on pet regulations by being able to compress in length from 22" to 16". The ends are designed to expand when there is nothing blocking them; they automatically fold down to fill the available space. You can also use it in the car, as it features straps on either side that are made for a seatbelt. There's also a super-plush removable foam bed inside that's machine washable, and you can even buy a warming pad as an add-on.