I could not find anything in the rules, but can anyone think of a reason why you would not get an attack of opportunity while prone? You would get the -2 to hit still though.
There's nothing in the prone rules which state you cannot take reactions or make strikes or anything of that sort. All it says is you receive the flat-footed condition (which is -2 circumstance to AC) as well as suffer a -2 cicrcumstance penalty to attack rolls. That's it.