Can I play lands from the graveyard more than once in a turn with Crucible of Worlds?
If you look at the Gatherer page for the Crucible, it tells you that


  Crucible of Worlds doesn’t change the times when you can play those land cards. You can still play only one land per turn, and only during your main phase when you have priority and the stack is empty.


(Emphasis mine.) So the lands played from the graveyard do not get a separate land-playing quota.