Mango Tango has some of the absolute best patterns for laptop bags I've ever seen. They have a wide assortment of colors, patterns and fabrics, so you're sure to find something you like. Fortunately, they aren't too pricey, ranging from $40-$60, and are available in not one but two sizes, 16" and 18".

My personal favorites are the pink faux-suede quilted, and the canvas striped bag, which reminds me of those retro bowling bags.

Visit their site to see the huge variety.