What is the best way to store fresh berries? I have been buying fresh berries from the store on the weekends, and am looking for the best way to make them last throughout the week for use as either a snack or as a component for salads.

The blueberries last the longest, and I can usually salvage enough by Thursday or even Friday, but the blackberries and raspberries seem to either get moldy, or turn to mush, before Wednesday is over.

I've been storing them in the refrigerator in the plastic vented clamshells they come in.  

Is there a better way of storing them that will extend their shelf-life another 1-2 days or more?
Store them unwashed. Take out any "bad" ones. I've had decent luck adding some paper towels to wick away extra moisture that seems to speed up the spoilage. Martha Stewart suggest going even further and spreading them out on paper towels on a sheet pan. I have no idea who keeps a fridge empty enough that they can store full sheet pans in there, though.

I've never tried this, but someone suggests washing it lightly in vinegar/water. *shrug*

Then of course, wash and freeze them spread out on a sheet pan (to make it easier to separate later). I assume this isn't what you want to do, but it is very effective, depending on how you plan to use them.