The basic command to read environment is /usr/bin/env.
It is possible to use /proc directory to find out path of any program. First you must know the process number - use ps command to get that. For example, if xterm is process number 1088, you can find it's environment with command
# more /proc/1088/environ
This does not work with daemon processes like xdm. To access environment of system processes or other user processes, root access is required.
To debug Netscape, you can create a script /tmp/test:
$ cat > /tmp/test
#!/bin/sh
/usr/bin/env > /tmp/env
^d
$ chmod +x /tmp/test
Then set some helper application, for example RealAudio, audio/x-pn-realaudio to call program "/tmp/test". When you try to browse some RealAudio link (something from http://www.realaudio.com/showcase), Netscape calls the dummy program that stores environment to /tmp/env.