Nothing today beats gigabit ethernet for moving data around the home. (While 10-gigabit ethernet is starting to make inroads in corporate environments, it's still too expensive for most homeowners.) Gigabit ethernet translates to a maximum throughput of 125 megabytes per second, but you'll rarely see that speed; this is about as fast as a midrange hard drive, although networking overhead will make gigabit seem slower.
The primary standard for gigabit today is 1000Base-T, or IEEE 802.3ab. 1000Base-T runs over twisted-pair copper wiring. If you plan on using gigabit ethernet, you'll need Cat 5e (Category 5e) wiring. (You can also use Cat 6 cabling, though that's overkill for gigabit ethernet.)
Be careful when buying Cat 5e, however--some cheaper cables labeled "Cat 5e" may not be solid copper, or may be smaller than the standard 24-gauge, and your throughput on such lower-cost cables may be reduced. Make sure you buy cabling from a reputable manufacturer, and take care to avoid the cheapest cables. The weakness of gigabit ethernet lies within its strength: It requires physical wiring. So you'll need to string Cat 5e to any room where you want that level of connectivity.
I'll say it up front: if you're planning on using Wi-Fi for whole-house networking, think again. While 802.11n sounds great--offering throughput up to 300 megabits per second, and no wiring hassles--it isn't ideal if you want to do lots of media streaming and moving big files around.
For example, in my home we have a Windows Home Server with several user accounts. We also use the server as a repository for applications. Installing large apps over wired gigabit ethernet takes only a little more time than installing from a CD. But installing software over an 802.11n link can take a very long time.
On the other hand, if you simply want to connect a small number of PCs, Wi-Fi may be the right way to go for you. Wi-Fi is a quick and easy way to connect several business laptops, Wi-Fi-enabled cell phones, and light-duty devices such as an Apple iPad or a netbook.
If you like the convenience of Wi-Fi for connecting laptops and phones, you might consider a mixed network, using a combination of Wi-Fi and gigabit ethernet. I'll discuss one possible scenario for a mixed-mode network on the next page.