If you have furniture style cabinets, or plan fancy window treatments, put electrical plugs above them.  

Put conduit runs in for stereo speakers for multi-zone sound around the house.

Wire for Ethernet.  10 years ago it seemed like wireless was going to blow Ethernet away.  Well, as of 5:35 last night I have 1Gbps fiberoptic service and the wifi router puts out 300Mbps theoretical, 200 Mbps actual standing next to it, and 150 in the next room over (will be pulling in Ethernet runs over the Christmas holiday in the 1986 house to get a 1Gbps plug into the network card of my computer).  If you can stand it put in the pex tube or whatever so you can pull ethernet wires out in 20 years and put in Fiber.  We went up 100x 56k dial up speed in 20 years, Ethernet is going to look slow soon.  Not sure how, but if you build it, someone will figure out how to use the bandwidth.