The way things are going for music retail, this category may be irrelevant by next year. So, all you holdouts from the MP3 revolution, enjoy SecondSpin's bounty of used CDs while you can. Because it offers the most money to patrons selling their unwanted compact discs, this Costa Mesa shop consequently has built a voluminous, strong collection of albums in practically every genre (metal, Latin and pop/rock are especially robust). While most of the used discs go for $6 to $10, hundreds are tagged for $3, and you can sample any CD before purchasing. SecondSpin's a great place to thriftily fill in the gaps in your collection, and as a bonus, it stocks tons of used DVDs and a few tables full of gaming-device offerings for PlayStation 2 and Xbox.