Safe solenoid driver: can I use a slow blow fuse?
Drive solenoids through a hardware monostable, so that they simply go off. 

It can be as simple as RC coupling the drive fet.







simulate this circuit &ndash; Schematic created using CircuitLab

An other approach is to sense the current drain into all solenoids, and if it stays on for too long, force a hardware reset on the CPU, thus (hopefully) releasing the drive. 







simulate this circuit

The reason for this circuit, was that it was an easy retro-fit to impact printers that would burn out the printheads when the cpu locked up. This circuit was added in series with the common wire, and connected to the reset pin.