felipeksw:
I'm planning a new project that will have 3 or 4 Arduino working stand alone and one Arduino like a data logger asking some informations to these Arduino.
If the slaves are active all the time, even when the master is not present, (so they can always be listening) then you could communicate between the master and the slaves using nRF24L01+ wireless transceivers.
When the master is switched on (or brought within range) it can poll each slave in turn to get data. There is an example of a master and 2 slaves in this Simple nRF24L01+ Tutorial and it could easily be extended to several slaves.
...R