depend on your OS and your available space http://yasirimran.wordpress.com/2008/04/27/tables-in-mysql/
well unlimited, depends on the space of the mysql database. some hosts restrict them, some not. tables arent a problem, its when they get filled, thats what takes up most space.
Theoretically, there is no limit. But practically, it depends upon your OS and Hardware. MySQL performance may degrade when you reach to a few gigs of data.