Multiple arduino Wireless communication
It really depends on the communication range and context required.

If your slaves are within 10-20 meters from the master device and the environment is not polluted (in terms of magnetic field) you can achieve good results with very inexpensive nRF24L01+ modules which operate in the 2.4GHz.

If you need to cover greater distances (in the order of 100 meters) or a polluted environment then you have to resort to shorter wavelengths or more powerful devices, but that brings in the question on how are you powering your slaves: on battery power those ranges get pretty power hungry.

Generally speaking I would say this question should be rejected as it's going to start a debate rather than provide a solution.

You can get some introductions on how to use nRF24L01+ modules simply searching online:


some posts on my blog
the Arduino library I always advice
a pretty valid guide