iTrailMap
They offer both a free lite version as well as a paid version which offers 3D maps. I use the lite version and it seems to do the trick.
As with the real life paper trail maps, some are better than others. Smaller mountains are easier as the map isn't so compressed. A resort like Killington or Sunday River can be tough.
Overall, if your pretty comfortable reading the classic "Jim Neuheus" trail maps, this app should work for you.
Enjoy!