Grapes, cut up apples, cheese, crackers, sandwich...
Bitterproffitt: Most packaged food is OK to bring back into the US. It's raw fruits/meat/vegetables/unpasteurized dairy that are not allowed. You can look up the exact rules, but I almost always return with a bag full of all manner of edible treats. If I'm at all in doubt about whether something is allowed, I ask at Customs and they either wave me through or take it away.