Ethernet in the walls is a definite yes of course.

A backup electricity generator would be cool if power outages aren't uncommon in your area. Something like a central UPS.

Good insulation is key. Double glazed windows, etc.

A solar water heater is a good idea if you get a good amount of sunshine.

Grey-water recycling is a good idea. You can also reclaim heat from it.

http://en.wikipedia.org/wiki/Hot_water_heat_recycling

A composting setup would be handy if you have a backyard or garden.

Choose robustness and longevity over style and minor cost savings for the various components/materials that will be used.