Top loader washing machine fill valve drips continuously
The Solenoid Valve is leaking.  It is an easy repair if you are comfortable with disassembly and re-assembly of the machine.

It should be about a $20-50 part depending on your machine.  It may be possible to replace the soft goods in the valve and repair it, but its probably not worth it as all the work is in taking the machine apart and putting it back together.