If you don't want to carry the sterlite medium show off you can get the BCW Comic Book Stor-Folio this can fit in your backpack and can hold 10 bag and boarded comics or 20 comics unbagged. You can find them online or maybe at your lcs.
Neat. I'll look into this. I always like to take comics to sign. I just got a ton signed at Calgary Expo last weekend. Incidentally, this is the first time I brought a telescopic art tube to a convention. I've been going to cons more and more and absolutely hate it when I get a poster, print, or piece of art and have no place to put it. Or worse, I would try to roll it up and store it safely in the backpack but it would always get crinkled. This has been a lifesaver and collapsed it even fit inside my backpack.
Also, if I am going to be far away in an auditorium it can be fun to carry a small pair of field glasses/binocs. At Calgary Expo, the only place this is really needed is in the Arena panels. Still, I suppose if you wanted to really see some cool costume up close, this would also be good for the costume contest there as well.
Camera, powerbars (food), water, well broken in/comfortable walking shoes. I also pay attention to the weather and if the con has a lot of stuff outdoors, ensure I bring either a hoodie, windbreaker or both.