Ok...here we go...
Haste and/or boots of speed add one attack per round
Improved haste doubles your attacks per round (for a max. of 4 in a round, I think...).
Hope that helps! Keep in mind, however, if you have the ring of free action on or have cast free action upon someone...they will not be able to use the boots of speed. Free action disables *all* magic that effects movement.
------------------
Now where did I leave that doughnut?!