build a 32.768kHz oscillator circuit that can output CMOS or TTL levels. You can buy the complete unit or build one using a 32k crystal. Once you have that, run it into a digital divider circuit that will divide it by (2^15) then output that result and you will have a clean, precise 1Hz clock.
The 60Hz method can work (using zero crossing detectors) but since you didnt mention how "precise" you need it, the crystal is the way to go. BTW, you dont need 32k, you could use any value that is divisible by a power of 2.
I think the power company regulates the 60Hz to something like 60Hz +/- 0.001 Hz.. maybe that is good enough for you - I dont know.