By the time I ordered, Google Play, Amazon, and others were already sold out. I bought my Chromecast from Best Buy, mainly because a local store had one in stock I could pick up today.
The package was very reminiscent of something you'd get from Apple. Small and clean although not quite as minimalist in art as something from the folks in Cupertino.
Side note: I love disclaimers.
Back to the install - My HDTV is almost "old" by HD standards, but it does have an HDMI port on the side, which I previously used for a DVI-HDMI cable from my MacBook. Newer TVs may have HDMI 1.4 ports, which can power the device directly. I wound up plugging the Chromecast into the wall via the mini-USB-to-USB power adapter, included in the package.
You do need either a Mac or Windows box or an Android device for initial setup; can't do this with iOS just yet. That said, configuring the Chromecast to connect talk to my MacBook and the network was easier than I expected it to be.