If you're operating off a laptop through something like Pronterface, I think that shows the last line of Gcode that happened before it crashed, so you can use the exact same G-code, and just resume from where it stopped.

I haven't any experience with this though. It's worth noting that if you're printing with a heated bed, the print can pop off the bed as it cools off, completely ruining your chances of resuming it. Otherwise, if you're printing ABS, the last printed layer could have cooled so much that prints are likely to be weak at that point.

There's is also sometimes a slight deformation/gap where it resumes due to some plastic oozing out of the nozzle as it heats up (which forms a blob if you don't wipe it off, and a gap if you do). When resuming, I try to preheat the nozzle to temperature, expel some filament, and quickly resume before it oozes too much.