If you're in Scotland or the North of England then to crack means to chat or to gossip.
If you cracked open a bottle or two while you were chatting then crack hearty (in NZ and Oz that means put on a brave face): that headache won't last forever.
If missed the crack of dawn then you'll have to get cracking, and if the others are still yawning then I suppose you'd better crack the whip (but crack a joke and a smile while you do it or someone might crack you over the head).
Crack a nut, crack a riddle, crack those crackers you forgot all about on Christmas Day, perhaps even crack a wave.
Crack up, crack down, crack on -
But just don't crack!
Thing To Do Today: crack. This word comes from the Old English cracian, and is related to the Dutch kraken and the Sanskrit gárjati, which means he roars.