for a WiFi adapter that supports the RTL8192cu chipset, as both the
latest Raspbian and Occidentalis distributions both have support for
this built-in and we've found its much faster than the Ralink chipsets
If you already have a WiFi adapter, just give it a go, even a lot of the very low cost budget adapters will work without any trouble.
does however use quite a lot of power, so check the power rating of
your power supply. Some WiFi adapters require an external power supply to work well. We suggest the 5V 1A power adapter in our shop if this is the case. All of the WiFi adapters we have in the Adafruit shop will work just fine this way.
If you have a WiFi adapter plugged in, then you no longer have two free USB sockets available for your keyboard and mouse, so you may also need a powered USB hub.