Club Penguin now works again! Clear your cache if you are still having issues.
By the looks of it Club Penguin is having some loading issues for everyone. When trying to log in (past the login screen page) it says Load Error: Sorry, there’s been an error loading Club Penguin. Please try logging in later. If the problem continues please contact email@example.com.
Also, when looking at some backend changes, for some reason they removed all the stamps from their game file. (on accident and they should be re-added once the game is fixed)