The ISE Design Suite 11.4 update is now available. To update your existing ISE Design Suite 11 installation, run "XilinxUpdate" from within the ISE Project Navigator or visit the Xilinx Product Update Site.
New installations require the ISE Design Suite 11.1, available at the Xilinx Product Download and Licensing Site. You will then need to install the ISE Design Suite 11.4 update described above.