Many other tools are listed on the eedesign Web site: www.eedesign.com/resources/opensourcelinks.html. And others on the Hamburg VHDL archive: tech-www.informatik.uni-hamburg.de/vhdl. One more great VHDL page: www.angelfire.com/electronic/in/vlsi/vhdl.html. Also look at the comp.lang.vhdl newsgroup.
Transient Research, home of Octave-MPI: www.transientresearch.com/d-octave
Alessandro Rubini and Jonathan Corbet. Linux Device Drivers, 2nd edition. O'Reilly and Associates, 2001.
FreeHDL: www.freehdl.seul.org
GHDL: ghdl.free.fr
Altera: www.altera.com
Octave: www.octave.org
Xilinx: www.xilinx.com
How to get Quartus and ISE running on Linux: www.polybus.com/xilinx_on_linux.html