Last year we had Postcards from Penguin (I'm using mine as bookmarks and to send to friends), but now - and even better, I think - we have Postcards from Puffin: 100 Book Covers in One Box, and what favourites are among them! Too many to show individually but I've put a few together to give you an idea of what's included and there are more over here. Don't they bring back memories?
Watership Down, The Lion, the Witch and the Wardrobe, Peepo ...
The Hobbit, Paddington, Swallows and Amazons ...
Roald Dahl, E. Nesbit, Frances Hodgson Burnett - I want to keep all of them so I think I'll have to buy a second set to give away.
Last year, demand for the Penguin ones greatly exceeded supply; let's hope sufficient sets of the Puffins have been printed so everyone who wants them can get one.
Edited to add: re. Iris's comment on online availability, Amazon UK has them, as does The Book Depository, while Amazon US look to be getting them sometime.