http://couture.zappos.com/ - footwear for men and women. Designers: Celine, Marc Jacobs, Kate Spade, etc.
http://www.saksfifthavenue.com/ - sells shoes from Jimmy Choo, Dior, Prada and other great designers.
jildorshoes.com - shoes, boots, pumps and sandals from many designers including Chloe, Joicy Couture and Kate Spade.
shoefly.com - huge selection of designer shoes. Brands: Ugg, BCBG Max Azria, Dolce Vita, L.A.M.B, Converse and many more.
bloomingdales.com - has also a wide selection of shoes from such designers as Michael Kors and Marc Jacobs.
And last, but definitelly not least, we have www.eluxury.com and www.net-a-porter.com. These are, probably, the most well-known online stores for designer products.
So, if you have loads of spare cash that you just feel like spending, go visit these stores and.. well, knock yourself out! ;)