At each compilation, those files are different (most include a timestamp)
List made the 22 feb 2009 on arch i486

/boot/System.map
/boot/System.map-2.6.27
/boot/vmlinuz					symlink to /boot/vmlinuz-2.6.27
/boot/vmlinuz-2.6.27				contain the timestamp seen with uname -a
/lib/udev/devices/core				link to /proc/kcore (the memory space)
/lib/udev/devices/stderr
/lib/udev/devices/stdout
/root/.gnupg/trustdb.gpg
/usr/bin/nano			nano --version		GNU nano version 2.1.6 (compiled 15:14:39, Feb  8 2009)
/usr/bin/ntpq			ntpq --version		ntpq - standard NTP query program - Ver. 4.2.4p6
/usr/bin/ntpd			ntpd --version		ntpd - NTP daemon program - Ver. 4.2.4p6
/usr/bin/vi			link to vi
/usr/bin/vim			vim --version		VIM - Vi IMproved 7.2 (2008 Aug 9, compiled Feb  8 2009 14:09:11)
/usr/lib/perl5/5.8.8/i486-linux/Config_heavy.pl		contain uname -a, configuration time,...
/usr/lib/squid/ntlm_auth
/var/cache/ldconfig/aux-cache


Those files md5 do not vary on the same machine but depend of the building machine
/etc/mtab				depend on the devices/partitions mounted on the building machine
/etc/pango/pango.modules		order of the modules list vary from machine to machine (locale?)
/lib/libc-2.7.so			contain kernel version '2.6.18-6-686'
/lib/libc.so.6				symlink to /lib/libc-2.7.so
/usr/lib/perl5/5.8.8/i486-linux/Config.pm	contain kernel osvers => '2.6.18-6-686'
/usr/lib/perl5/5.8.8/i486-linux/Errno.pm	contain kernel osvers => '2.6.18-6-686'
