Since my previous post on using Doxverilog, there have been a number of updates. Here's an updated installation guide for version 2.8 (patches version 1.8.5 of Doxygen). It has been tested on RHEL 5.7, using SVN version revision 85. The ZIP file found on BerliOS seems corrupt (at time of writing), so use SVN as shown below.
svn checkout svn://svn.berlios.de/doxverilog/trunk
gtar zxf doxygen-1.8.5.src.tar.gz
cp trunk/doxverilog/Doxverilog2.8/sources/* doxygen-1.8.5/src
cp trunk/doxverilog/Doxverilog2.8/verilog.patch doxygen-1.8.5
patch -p1 < verilog.patch
make all |& tee ../make.log
Again, the above is tested on RHEL 5.7. If you run into issues on Ubuntu 14.04, check this.