A beekeeper near here who runs a bee supply business sells sodium nitrate
fertilizer for use in smokers (in small quantities in addition to your
normal smoker fuel)  I also found out (from this list) ammonium nitrate
fertilizer also works.  I tried this once or twice on a particularly
ornery hive and it does work.  Don't use too much of these, they're oxidizers
and accelerate burning, producing LOTS of smoke for a short time, then the
fuel's gone, or maybe a fire if things get out of control.  Be careful of
this smoke, while it's largely laughing gas (guess bees like it too!) it
also contains nasty stuff.
 
-Mike