Background I recently bought an ACR122U reader  to play around with RFID, and especially MIFARE Classic cards because of their low security     and widespread adoption. The different sectors of the MIFARE Classic card are protected by different keys. To be able to decrypt the content of the card, the keys must be found. There are two well-known applications for this: mfcuk  and mfoc . A typical attack scenario is to use mfcuk to find the first key of the card (which may take quite some time).
Preparing the USB stick The first step was to prepare a USB-stick with the XenServer 6.2 ISO downloaded from http://www.xenserver.org. Since my workstation runs Linux, I initially tried using dd, but my server refused to boot from the USB stick. After trying virtually every guide on the Internet, I could finally put something together that worked. On my home computer I run Arch Linux, some paths in the commands below might have to be adapted for your system (most probably the /usr/lib/syslinux/bios paths).
EDIT 2013-11-24: As of kernel 3.12, the driver has been included in the staging area of the Linux kernel . Upgrading your kernel to get the included driver may be easier than compiling your own kernel module.  http://kernelnewbies.org/Linux_3.12-DriversArch#head-535f1b62f845d5e0d9d20c2980ab6b35525f67c5 So I recently bought a TP-Link TL-WN725N wireless adapter to use together with my Raspberry Pi. The main reason to buy this particular model was that it should work out of the box together with the Linux kernel in Raspberry Pi.