The wackiness never ends in the world of subways. The original MTA Service Advisory here.
The A,C: After an Easter respite, Chaos returns to the blue line for the next four weekends. NO SERVICE between Jay Street/Borough Hall and Utica Avenue. None. Nothing. Nada. Well, just a free shuttle bus. They claim there will be some nonstop buses between Jay Street and Utica Ave. They claim that the shuttle bus trip between those stops should be around 20-30 minutes depending on "traffic conditions". They also claim to have seen Bigfoot and the Jersey Devil playing bocce in Squibb Park. Read the MTA service advisory for more details.
And, of course, The C won't be running at all.
The N, R: All Brooklyn-bound trains are skipping the Court and Lawrence Street stations in Brooklyn, as well as City Hall, Rector, Whitehall street stops in Manhattan. They are being rerouted from Canal Street to DeKalb Avenue. Best to jump on the 4 to Borough Hall if you want to get out at Court or Lawrence.
The 4, 5: Manhattan-bound 4 trains are running express between Atlantic and Utica Avenues. If you are going to the Brooklyn Botanic Garden for Cherry Blossom Season, jump on a 2 train instead.
Both 4 and 5 Manhattan-bound uptown trains will be skipping Fulton Street.
The F: Coney Island-bound trains will be skipping 4th Avenue, Prospect Park, and Fort Hamilton Highway stops. However, 7th Avenue is safe.
The Q: Manhattan-bound trains will run express between Kings Highway and Prospect Park. Every local stop in between is screwed. Consult the MTA Service Advisory for tea and sympathy.