I have a gyro sensor, xbee module, motor controller, and servo controller all hooked up to an arudino which i have migrated from the duemilanvoe baord to a bread board (breadboard has the resosontaor and arduino seems to work very well). Now all my componenets are rated for 5 volts and require very little current (every component has a different current rating). So i decided to put everything in parallel. I have also made sure that the battery can provide the correct voltage and current. Now i thought that by putting everything in parallel and using resistors i could control the current to the components. However, the sensors themselves have resistance. So how can I pick the resistor size without knowing the resistance of the sensors??? There is nothing really on the spec guides of the sensors. Another thing to point out was that I hooked everything in parallel to a 5v and everything seemed to work. I checked currents at each of the sensors and they were all correct. How is this possible?
If all the sensors and the processor are five volts, just put them in parallel, make sure you've got decoupling, and forget about it.
You don't need to control the current to the components - they'll take care of that by themselves.