Zoweetek 600Mbps Mini WiFi USB Adapter is a good USB adapter that is compatible with most any operating system from Windows to Linux.
It works with:
Windows XP/Vista/Win7/win8 and 8.1
Linux and Macintosh
The package comes with the dongle, driver disk, and instructions.
*The instructions is step by step on how to install the drivers and get everything connected and it is mostly pictures so you cannot get lost
It is a dual band USB adapter and works in both the 2.4Ghz and 5GHz bands.
It has support for the new 802.11ac protocol.
Speed: 433Mbps for 5Ghz network and 150Mbps for the 2.4Ghz
Frequency: Dual Band 2.4GHz and 5GHz
This thing works for any network and it is future proof for when you get 5Ghz if you don't already have it.
For just under 16 dollars this thing cannot be beat.