Layout & Routing Tools
For layout take a look at Electric(http://www.staticfreesoft.com/).Electric has recently been ported to Java. One nice feature is that it can route standard cellsusing a VHDL net list. Electric can do much more so be sure to visit the web site to get all the details!
There is also a free Linux tool called BECS that is quite nice. I have Virtual PC configured withRed Hat Linux and use BECS too. You can get it from: http://www.rubicad.net/.
The Alliance tools have also beencompiled on OS-X 10.2 and higher. Alliance is a completeset of free CAD tools and portable libraries for VLSI design.It includes a VHDL compiler and simulator, logic synthesis tools,and automatic place and route tools. A complete set of portableCMOS libraries is provided. Alliance is the result of a twelveyear effort spent at ASIM department of LIP6 laboratory of thePierre et Marie Curie University (Paris VI, France).
Another layout editor that I reallylike is from DesignWorkshop Technologies. The dw-2000 layout editor is available on severalplatforms but unfortunately the Mac version only runs on OS-9.However, even on OS-9, this is a very full featured layout editorthat is well worth the commecial price! Take if for a test drive.