Over the ten years of owning my 2004 Acura MDX both the front and rear blower motors have stopped working. The air conditioning also stopped working but that was a different problem where the clutch seized up.
Anyway, both blower motors had the same problem, their thermal fuses burned out. I purchased replacement thermal fuses from DigiKey for about $.75 and thermal paste from Radio Shack.
Unfortunately the front and rear thermal fuses are in quite different places but I found excellent tutorials for the front thermal fuse here and for the back fuse here.