You can make ranged attacks from a mount almost as well as you can from the ground.
Prerequisites: Ride 1 rank, Mounted Archery, Mounted Combat.
Benefit: The penalty you take when using a ranged weapon if your mount is taking a double move is eliminated, and the penalty for using a ranged weapon when your mount is running is lessened from –4 to –2. You can attack at any time during your mount’s move.
Special: A fighter may select Improved Mounted Archery as one of his fighter bonus feats.
Source: Complete Warrior, page 100.