The EqLocate program allows you to select P-wave arrivals of a number of seismograms for an earthquake and find its location.
The package contains several earthquakes which you can use for practice. To use you click on the P-wave arrival on each station and then guess at the epicenter. You will be shown lines toward each stations from the selected epicenter which will guide you toward your next pick. The RMS error is displayed in text at the top of the screen plus colored dots will record your past guesses.