Ithaca Farmer's Market - Saturday is the big day for this one in the summer, though also open Sundays and Thursdays. Lots of fresh, local produce. Trumansburg has a farmer's market on Wednesdays, 4-7 P.M.
Wegman's - The "destination resort supermarket". They have everything, if you can only find it. In-store prepared foods are quite good for an easy take-out meal. Closer by is Sur-Save on Rt. 96, south of Trumansburg.
Brownie's Corn - fine corn and vegetable stand and quite close by: on Rt. 96, north of Jacksonville.