Oh, man, don't you just love those things!!! I use them all the time. In fact, I have one comforter sized one sitting next to me that holds all my misc yarn. It's easy to squish it around to see what's in there.
As for toting projects around. I just use those free bags you tend to get with makeup or book purchases. I have several I picked up at a career fair. If you live somewhere that has a big "market" type street (ie. Chinatown), like San Francisco or New York, you can pick up one of those giant tote bags for a few bucks and they usually have a simple little pocket on the outside and zip or snap up on the top.
I don't make my own totes, because the yarn it takes to make a tote is just to heavy to be lugging around more stuff in, especially as the project gets bigger. Also, if you're going to be carrying around hooks, the bag will either have to be lined or you'll need a smaller carry pouch to put inside it so the hooks don't fall through the stitches.