Whilst it they might "look" like a resistor, but they are very much a non-polarized capacitor used for stopping noise and reducing spikes created. Also known as "Decoupling capacitor" ([link=http://en.wikipedia.org/wiki/Decoupling_capacitor]wiki[/link])
Further images & comparative graphs (with/without) [link=http://www.seattlerobotics.org/encoder/jun97/basics.html]here[/link]



Bypass capacitors
When driving an inductive load such as motors, the load sometimes generate noise back to the board. This noise can mess-up the power of the board. If this happens, you need to add a small capacitor across the motor leads.

A typical bypass capacitor size is 0.1uF (0.1 Micro Farad). Don't use polarized capacitors (i.e. ones that have one lead longer than the other).


My white-motor Suntech's have 2 x 0.1 uF (100000pF) "104" capacitors for this function.