What is stiff about the gloves?  If it is the palms, and they are leather,
a good glove oil like you would use on a baseball glove would be OK.  I
always buy gloves with the "Durasoft" palms.  It is an artificial material
that wears better than leather, doesn't get hard from sweat, and requires
no break-in period.  If the stiffness is in the cuff or fingers, the gloves
may not be the right size for you.  If the cuff is causing the problem, try
some larger gloves, and if it's the fingers try smaller gloves.  Some stiffness
is OK because it helps protect against wrist and thumb injuries.  You could
also look at the short cuff models, ala Mario, but there you are sacrificing
protection for range of motion.  I would stick with the long cuff, unless
you never expect to take a two-hander across the wrists.
 
-John Hughes