FLizarraga
I would also divide these as to whether or not there are developed systems, often moving across similar methods. I tend to see 'oracles' as stand alone decks, generally the creation of one or two people.
However tarot, I Ching, Lenormand, runes etc have systems developed over time by many people and the systems still hold over variations in their representation.
But they are all oracular, systems or stand alone. imo anyway.
The word "oracle' is used commercially for those decks Alta speaks about --can't define it better. And a lot of those are indeed rosy-colored and have a high sugar content, as Le Fanu rightly points out. But of course not all of them are created equal.
However, GotH points out the original meaning of the word.
Maybe I'm not understanding something here as there seems to be a partitioned distinction on this site about tarot and oracles. I thought an oracle was any tool or portal by which information was given by "the gods." So wouldn't tarot be considered an oracle as well?
So there's the commercial 'oracle' designation and the original 'oracle' designation, according to which --as gregs points out Socratically-- Lenormand, Tarot, the I-Ching, the African Ifa, are structured, long-standing oracular systems, as the Pythia was. Just my two cents.