http://www.mega.nu/traj.html
JBM Trajectory Calculation Page. As stated in other posts, there are certain things you need to know for this to be useful for you. But, gather the Actual data required fill out the form and it will calculate Trajectory, Drift, Lead, etc.
You can also run multiple for different elevations, shooting angles, etc. to compile the data required for making longer shots.
MAKE NO MISTAKE: YOU WILL NEED TO VERIFY THIS CHART IN THE REAL WORLD PRIOR TO SHOOTING ON GAME. However, once verified and you know it's right, it will put you on target.