Before vacationing with my husband's family, I made souvenir beach bags for each of us to tote around while we were in Hawaii. I got the canvas bags at H&M (Muji has offers a similar inexpense alternative) and personalized them using t-shirt transfer paper. I created the design in illustrator, but it could be done in any computer program. Just remember to reverse (mirror-image) your design before printing it!
This is a great way to personalize bags for kids too. I picked up some Lands' End-looking bags at the dollar store and made pool bags for my kids. Now they can carry their own towels, snacks and goggles to the pool!