If I'm going to use some undercabinet LED fixtures like those from environmentallights.com, does the wiring for each strip go back to the driver or do they get connected to each other end-for-end in a serial fashion? Clearly you can physically connect more than one light together to form a longer strip, but I assume the same is done with short jumper cables too?

For example if I have three 27" uppers in a row and I install, say, a 24" strip under each do I just drill a hole through the "fence" between the cabinets near the ends of the strips, run a short cable through, and connect each strip to the one in the next cabinet effectively making one long strip of 36"? Not having to run a wire to the back of each cabinet to go to the driver would keep things tidy.

Or... it just occurred to me that instead of drilling a hole for the wire I could cut a notch in the fences so that one long light strip could actually span multiple cabinets? That way I could use the longer strips and avoid the cost premium of the shorter ones? It would also make the light more consistent without the breaks between light strips. I'm liking that idea!

You could drill a hole through the intervening fences or notch the fence. Nb - check with your cabinet maker.

Btw, the strips are also sold by superbrightleds.com ...

Drill a hole.
Use a longer drill bit and a drill with minimal top clearance to make the angle as shallow as possible.