As a warning more than a hint, it is not advisable to change the names of Apple's .pkg files. A friend of mine had backups of all generations of iApp releases. Finding himself with, for example, two packages called "iTunes.pkg," he changed one to "iTunes 2.pkg" and the other to "iTunes 3.pkg."
Later, when trying to install one onto another machine, the installer returned the error "Could not find valid Bill of Materials file." Turns out there is a file in the package contents named "iTunes.bom," and the package name has to match this to install. So, if you ever do change your .pkg file names, remember to change them back before you install again.
[robg adds: If you can't remember the original name, just mount the disk image, control-click on the package, and navigate to Contents -> Resources to see the .bom file. The name of this file is what the name of the package should be. I haven't tested this hint -- if anyone happens to be installing something, please confirm via a comment.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2003030321162054