Unless you feel up to performing surgery on the unit, potentially replacing externally-accessible parts, I'd write it off. A whole host of things could have happened, and each one is a different fix. For example, the PCB on the drive could have cracked or otherwise have been damaged, effectively killing the drive. The external solder joints (or wires) between the PCB and the spindle motor could have been damaged and current isn't able to get through to power the spinup. The platters and/or head assemblies (actuators, etc.) could have been damaged.
In all honesty the data is probably fine, so if you want, you could probably cough up the money to have it professionally retrieved. That isn't cheap, though. From experience I can tell you it's much cheaper in the long run to just buy and use a backup solution (second drive or whatever).
I hate to say it, but most electronics only detect and respond well to errors when they're initializing. Once up in operation, very few have logic built in to monitor operation and handle problems. Things are slowly getting more intelligent, but by and large the only event during operation that all devices in a computer handle well is the POWER_OFF signal. You can bash drives with hammers or set them on fire and they'll keep happily trying to run with horrific damage. Turn them off and then back on, however, and either the damage will be too much or the init process will flag the errors and prevent operation.