Even though iTunes is backing up all my contacts while I'm syncing, the backup still exists on a computer. So I would like to make a backup on another physical medium, just in case my computer or iPhone gets destroyed, lost, stolen, etc....
How can I do this?
You can export your contacts from the
File < Export < Contacts Archive
This of course only works if you sync your iPhone's contacts to your Address Book app.
Another thing to try is syncing with iCloud, which will back-up/copy your contacts (among other items on your iPhone) into the Cloud and you could access it anywhere where you have an internet connection.