These cheerful oh-so-summery fruits fall into three categories: sweet, sour and middling sweet-and-sour. Common sweet varieties are the deep burgundy Bing and the two-toned Rainier; both are naturals for eating fresh out of hand. Pitted cherries can be tossed in fruit salads, flambeed with rum or brandy, or baked in cobblers, custards and, of course, pies. The dusky red sour cherry has a short season (up to four weeks in good years) around mid-July. Raw, their complex, tart flavor is an acquired taste, but when cooked they are perfect for pies and preserves. Varieties like Montmorency and Meteor bridge the sweet-tart gap. If you're unsure which camp a cherry falls into, snag a taste before buying. Buy cherries that look plump and are free of cracking, splitting or blemishes, and choose those with supple green stems, if you can. All red varieties should have a deep, uniform color. Fresh cherries should be refrigerated and eaten within a couple of days after purchase.