How many ceiling fans and switches can I put on one breaker
There should be no problem running 4 ceiling fans on a single 15 ampere circuit, though it will depend on what else is on the circuit.

Say a 52" fan is 90-100 watts (at high speed), plus three 60 watt bulbs. That puts each fixture at 280 watts or so. Which means four of them, would be 1120 watts. 

A 120 volt 15 ampere circuit, can supply 1880 watts (120 volts x 15 amperes = 1880 watts). Some folks will argue that you should only load the circuit to 80%, so that would be 1440 watts for a 120 volt 15 ampere circuit. Which even so, is still enough to supply the fixtures.

Note: the values used in the answer are an estimate, for example purposes only.  Check the listed wattage for the devices you'll actually be using.