Every day brings something new on Pinterest. But, some things take on a life of their own and just keep on keeping on.
Telling what is popular on Pinterest is not an easy task. There are no publicly available statistics tools yet. There is a "Best of Pinterest" page, with information culled from Pinterest's 19,858,832 users, that offers insight into what is important to Pinterest's biggest demographic, women ages 25-44.
But, those results are based on "repins" - that is to say, how many times a particular item has been re-shared from its originally-pinned form. If that item had been pinned by 20 different users, there are 20 different versions floating around on Pinterest, all being re-pinned untold numbers of times.
This is different from the Facebook way of sharing. If my wife finds a link to share on Facebook, then I find it independent of her later and also post it, Facebook recognizes that we both shared the same link. Pinterest apparently does not.
All that to say, there may be things that are cumulatively far more popular than the items below, but there is no way of knowing that yet. So, with the tools we have available so far, here are the Top Five Most Repinned Items, as compiled on Pinterest's Best Of page (click each picture to go to its Pinterest page and get more info):
52,925 repins - Poster
25,819 repins - MegaCloset
25,177 repins - Paris
25,161 repins - Recipe
22,089 repins - Kids' Market Play Area