Is there a portable timer interrupt library?
I think it would be hard, or impossible, to make such a library. Already there are problems with pin-change interrupt libraries, and Software Serial (which uses pin-change interrupts).

Plus, to have a generic "callback" might tempt people to do things which they shouldn't anyway in an ISR, like do serial printing.

Let's say you choose to use a spare timer (eg. Timer 1). You have the issue now that you won't be able to do (some) PWM output because that uses Timer 1.

The closest would be to lever off the existing millis() code and just have a test in loop to see if the time interval is up, and then call a function - however that wouldn't be an ISR.