crocheted plarn bag by Thoughtful Rose, she used loops of plarn, and a size H crochet hook. Tight, dense stitches are the key to a plarn bag that won't stretch out of shape (that, and crocheting through both loops). Plarn is yarn made from plastic bags
Crochet in Color: Lots of Free patterns. I always go with the smallest hook for baskets, bins, etc. More useful if you don't have to shape them. The only time I use a bigger hook is if slouchy is what the design calls for. Make Crocheted Baskets!