long range shooting simulator on the interwebs. Granted any simulation cannot replicate actual training but some simple concepts can be learned.
This simulator can give you a basic understanding of estimating ranges using a mil or moa reticle and using a range card to set elevation and windage.
The main lesson this thing can show you is how to use the tics in the reticle to estimate the distance to the target based on the size of a known object, (like the poor schmuck in the sight picture).
Nothing can replace actual range time. Better yet, actual training with an experienced, professional instructor.
--Besides, actual range time is way more fun!