This would depend on your wiring configuration...
http://www.homewiringandmore.com/swi...3way/3way.html
check the above 3 way switch options and compare to your own configuration.
To have unswitched power onward , you must have an unswitched hot, & a ungrounded leg {aka neutral} wire available at the location you wish to run from. If you have these wires available then you may continue to an independent set of 3 way switches controlling a different fixture.