Venice Beach, Los Angeles
Save your money and buy all those vacation t-shirts, postcards, and trinkets at Venice Beach. It is the cheapest place for everything from t-shirts to vintage clothing. It's also an awesome place just to hangout because of the great beach and friendly people. If you're lucky, you might be able to participate in the weekly drumming party on the beach where anyone with a drum and join in.
What to buy: Everything.
What to pay: Shop around, and you can probably bargain.
Most of the shops are "open air" type places and offer a vast variety of things. The places are good for souveniers and all kinds of items to take back to a friend. Don't buy anything from an Englishman wearing an Oregon sweatshirt.
What to buy: Venice Beach is the place for T-shirts of all kinds,sunglasses,footwear,swimwear, watches,leather goods,rollerblades,and every kind of trinket you can imagine.
What to pay: Prices are pretty good, but beware that the quality can be questionable. Compare before you buy.