I'm trying to find a single term for a display of cards that a player can pick from. The most obvious example would be the 5 cards turned face up in Ticket to Ride. I thought there was a term for this display, but the rules just seem to call them the "face-up" cards.
Although this is a common game mechanic, each game appears to use its own term for such a thing, rather than any commonly-used term.
Fabled Fruit calls it the "Market". This term is quite generic and would lend itself to be used in any game if you wanted.
Splendor is the same as Ticket to Ride; just calling them "face-up development cards in the middle of the table".
Space Base calls it the "Shipyard", as a more thematic version of a "Market".
Ascension calls it the "Center Row".
Lost Ruins of Arnak uses "Card Row".
Clank calls it the "Dungeon Row".
These are just the first several games I was able to think of that use such a mechanic, and I was unable to find any common term used in more than one game (unless you count "row" as part of the name).
While individual games may use their own (usually thematic or contextual) word for such an layout, one generic term for this would be tableau, as in a static display of various objects, like that seen in Ticket To Ride and games listed in another answer.
Also applicable is array, though this feels more appropriate if the cards were in multiple rows and columns, such as in the game Kemet.
I like a lot of the other answers. Another potential generic term is Pool, as in "the card pool".
One definition from Merriam-Webster is - a readily available supply