I always have placed the electrolytic between my main rails... you should keep the 0.1uF's on the IC (someone should verify that), and stick a 10uF electrolytic between your gnd and main power line that goes to your servo, motors, etc. If you have separate power lines for the servo and motors, make sure each is decoupled separately (each has its own 10uF electrolytic) - this should minimize the noise in your circuit down to a respectable level.