The Hairpin has invented the Shopping Bracket (pdf) to help women optimize their purchasing power:
Open a tab for every online shop you like. Go through each tab and put everything you like even a little bit into your virtual cart no commitment to purchase is necessary.
Then force yourself to choose between things, over and over for hours, until it's all the way down to just two items, at which point I usually spend a few minutes mumbling pros and cons before closing the window altogether and basking in a deep sense of relief. And voila! You now have all the endorphins of a full-fledged shopping trip without having spent a dime.