I downloaded wxWidgets and compiled it (which took some hacking and a fix to one of the include files in world) and installed it. Then I tried to build Bitcoin and got this error:

g++ -c -O2 -Wno-invalid-offsetof -Wformat -g -D__WXDEBUG__ -D__WXGTK__ -DNOPCH -DFOURWAYSSE2 -DUSE_SSL -I"/usr/local/include/wx-2.9" -I"/usr/local/lib/wx/include/gtk2-unicode-debug-static-2.9" -DGUI -o obj/util.o util.cpp
In file included from /usr/local/include/wx-2.9/wx/defs.h:26,
                 from /usr/local/include/wx-2.9/wx/wx.h:15,
                 from headers.h:30,
                 from util.cpp:5:
/usr/local/include/wx-2.9/wx/platform.h:256:22: error: wx/setup.h: No such file or directory
In file included from /usr/local/include/wx-2.9/wx/platform.h:711,
                 from /usr/local/include/wx-2.9/wx/defs.h:26,
                 from /usr/local/include/wx-2.9/wx/wx.h:15,
                 from headers.h:30,
                 from util.cpp:5:
/usr/local/include/wx-2.9/wx/chkconf.h:94:9: error: #error "wxUSE_ANY must be defined, please read comment near the top of this file."

This is only the start of several screenfuls of errors ending with gmake giving up. Did I misinstall wxWidgets?

I also notice that makefile.unix has hardcoded paths in /usr/local/include/. If wxWidgets were installed as a package, the include files would be in /usr/include or /usr/pkg/include, depending on the package manager. Could you set the build process up with cmake or autotools so that they would find the right include paths?