Modcloth is a great online retailer. They carry clothes in a variety of sizes and price ranges, and their customer support is excellent.
Whenever I shop at Modcloth, I find that they always have a great selection and reasonable prices. They have an alternative and sometimes hand-made feel to them. I can always count on Modcloth to have ladylike and fun clothing.
Their shipping is reasonably fast and their shipping and exchanges are free and there is never any hastle with returns. They often have sales and promotions, which is great because their prices are occasionally a bit high. Well worth it for cute, unique looking clothes, though!