Decoupling capacitors in MCUs
Analog devices has a great app note discussing, not only the value, but capacitor type, as well as component placement. http://www.analog.com/media/en/training-seminars/tutorials/MT-101.pdf

To your questions... Small capacitors react faster to high freq than multiple large ones would in series. From this perspective, having 3 caps in parallel (10pf,10nF and 1uF) might look like you have an equivalent  large cap of 1.001001 uF, you essentially have 3 lowpass filters of 3 different freqs...

Also, I do a lot with instrumentation amps and brush motors so I often use ferrite beads, with 1k impedance around 10kHz, in series to the power pin.