I love the simple, casual look of this Reversible Shoulder Bag pattern from Beth at Lula Louise. You'll find complete pattern and sewing instructions. The pattern can be scaled down to make a fun little bag with a shorter shoulder strap. She also has compiled a list of free patterns for knitted market bags.
Here is another shoulder bag tutorial from tiny happy. The Lindie Bag from Craft Apple. Cheap & Easy Fabric Grocery Bags from Wisdom of the Moon. And a whole page full of pattern links at Henrietta's Handbags & Purse Patterns which makes me listing more links kind of silly.