In a submission, I encountered the phrase "can of corn" as a baseball term; hadn't heard it before, so went and looked it up. Apparently it refers to a baseball hit in such a way that it's particularly easy to catch.
John Marshall, the Seattle Post-Intelligencer's "Answer Guy," says that there are several possible origin stories for the phrase. The most accepted one, he says, is this: In olden times, "[...] a grocer would use a stick to tip a can of vegetables off a high shelf, then catch it in his hands or outstretched apron."
A British site, The Phrase Finder, gives a somewhat different explanation: it repeats a story to the effect that the phrase refers to a shopkeeper lightly tossing a can of food to a customer, and notes that it's a can of corn because the outfield is sometimes called "the cornfield."
But the P-I answer sounds better-researched.
Also, the Phrase Finder answer claims that the phrase was first used by announcer Red Barber, but the P-I answer says it was first used in 1896, which was twelve years before Barber was born.