"A newer nomenclature has developed, where three numbers are printed on the body of the capacitor. The third digit in this case works like the multiplier band on a resistor; it tells the number of zeros to tack onto the end of the two significant digits. Thus, if you see a capacitor marked "151," it is not a precision component. Rather, it is an ordinary capacitor with a capacitance of 150 pf. In this nomenclature, all values are given in picofarads. Therefore you might well see a capacitor marked 684, which would mean 680000 pf, or 0.68 µf."http://www.play-hookey.com/dc_theory/capacitor_values.html
I got this doing a google search using string "reading capacitor values"
thats the basic premise, although there are exceptions to it, the third number denotes how many zeros to add onto the number before it and that value is then in picofarads (pf).