I would like to install some can lights in my kitchen and I'd like to know if I can power them from the GFI outlet circuit in the kitchen or if they should be powered from the other light sources in the room?

I also would like to install a can light (suitable for wet locations) above a shower and I have the option to power it from a GFI which controls a single outlet which powers a whirlpool tub or from an existing non-GFI lightsource in the room. THANKS!

Well to answer question one, code requires that you have these lights on a designated light circuit, so you would need to run them from your other lights and not the GFI receptacle. You should have no problem with this, just double check that the wiring sizes match your breaker sizes. (for example: 14 AWG wire: 15 amp breaker, 12 AWG wire: 20 amp breaker)and you should be set.
To answer question two, I'm not sure of what code requires now of lights in wet locations (like the shower) but I think you still need to have it on the circuit with your lights, you will get more answers later.
Hope this helped, Kyle.

That is what I sort of assumed... THANKS for the quick response and confirmation!