Just a quick note – the bag that practically defines value in budget carry-ons – the OPEC, is no longer available at Campmor, but OutdoorPros.com is selling it for $41.90 – still a steal at that price! See it here: OPEC @ OutdoorPros.com
12.5.2010 Update: OutdoorPros.com no longer carries the OPEC. Campmor now has a private label version of the bag available. It’s $39.98, and you can see it here: Campmor Essential Carry-On
3.5.2012 Update: Appears to be no longer available. Anywhere. However: check out the very similar but slightly smaller (18″) Goodhope Convertible, which sells for less than $30. I haven’t used this bag – if you have, please comment! Thanks to reader Kat for the tip!!