where to buy records (LP's) online?

This weekend I bought a nice new turntable, and am going through my 1000+ LP's. Does anyone know of a place online to buy used records? I'm not looking for audiophile, mint-condition quality, but something a little higher than the scratchy thrift store ten-cent record bin. Also- does anyone know where to find/buy new or reissues of classic records on LP? I see them all the time in record stores- you'll see "kind of blue", or "double nickels on the dime" reissued on LP. Where can we browse and purchase those online? Thanks for any help. andrew