I finished up a made to order back-to-school bags for a new third grader. I almost always choose peached canvas (it's soft) or duck cloth for backpacks and over the shoulder bags. The colours are limited (brown, grey, lighter brown, white, sometimes a pumpkin?) but the fabric is sturdy and washes well. I'm making the switch over to Kaufman organic canvas this year-- it's a little bit lighter weight and Bolt carries a nice range of colours.
I have it on good authority (okay, my own) that the new issue of Stitch that comes out in a few weeks, has a pattern for a child's backpack and another for a bento style lunchbag. While I didn't use a pattern for this bag, check out the pattern bins at Bolt to find patterns for the whole family. The Sale bins is busting full right now. Modern Domestic is hosting a class on Freezer Paper Stenciling soon (it's the technique I used to print the horse on the front of the bag). If you haven't stenciled this way before, you're going to be going through all your tshirts and bags to personalize them once you've learned.
There is a a big stack of snack bags to make this year, too. I'm using cotton canvas and regular weight cotton scraps-- these are from the Cosmo Cricket line. Amy's tutorial is funny and fantastic (check out the comment thread for waterproofing ideas), or you could seam together two rectangles and fold over with velcro. I prefer to throw my whole bag in the wash rather than wipe it out, which is what you'd want to do with coated cotton. Also, I know that cotton (or linen) is absolutely food safe, especially if you take it one step further and go for one of our organics. One half yard will give you 4+ bags. A fat quarter will give you at least two.
Labour Day, I am ready for you.