Update 2015.03.12 those instructions also work for Ubuntu 14.10.

Of course, there is also an official way to program a Xilinx FPGA: the Xilinx Plateform cable!
This interface has official Xilinx drivers for GNU/Linux, but they are out-dated. Better use the open-source one from Michael Gernoth, at [1].
After a make in the source folder, run the install script as root:
./setup_pcusb /opt/Xilinx/14.7/ISE_DS/ISE/
It will copy the library in ISE folder, move the cable firmware to /usr/share/, and create the udev rules in /etc/udev/rules.d/xusbdfwu.rules. The udev script uses fxload for firmware loading, and there is already a Debian package for it:
apt-get install fxload
After restarting udev with:
/etc/init.d/udev restart
...the USB adapter should be recognized, and the corresponding firmware loaded into it over USB.
[ 9466.632176] usb 8-3: new high-speed USB device number 13 using ehci_hcd [ 9466.764855] usb 8-3: New USB device found, idVendor=03fd, idProduct=000d [ 9466.764862] usb 8-3: New USB device strings: Mfr=0, Product=0, SerialNumber=0 [ 9466.795802] usb 8-3: USB disconnect, device number 13 [ 9468.748159] usb 5-1: new full-speed USB device number 4 using uhci_hcd [ 9468.891201] usb 5-1: not running at top speed; connect to a high speed hub [ 9468.909197] usb 5-1: New USB device found, idVendor=03fd, idProduct=0008 [ 9468.909204] usb 5-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0 [ 9468.909208] usb 5-1: Product: XILINX [ 9468.909212] usb 5-1: Manufacturer: XILINX
iMPACT will need libusb to connect to the platform cable:
PROGRESS_START - Starting Operation. If you are using the Platform Cable USB, please refer to the USB Cable Installation Guide (UG344) to install the libusb package. Connecting to cable (Usb Port - USB21). Checking cable driver. Linux release = 3.16.0-31-generic.
Install it with:
sudo apt-get install libusb-dev
Using iMPACT, the IDCODE can be requested:

References
[UG344] | Xilinx, USB Cable Installation Guide, http://www.xilinx.com/support/documentation/user_guides/ug344.pdf |
[1] | Michael Gernoth, XILINX JTAG tools on Linux without proprietary kernel modules, https://rmdir.de/~michael/xilinx/ |