Is there a method to export the URLs of the open tabs of a Firefox window?

Go to Tools > Options.

In the General tab look for the Use Current Pages button in the Startup section. When you click on the Use Current Pages button, all the URLs of the pages open in different tabs are copied to the Home Page text box with a pipe delimiter. Copy the text to get all the URLs.

The keyboard shortcut to simulate clicking on the Use Current Pages button is Alt+T+O+C (tested in Firefox 14)

I found an add-on called Send Tab URLs that copies the URLs of all open tabs with the intention of sending them by email to someone. This add-on also allows the target of the URLs to be the clipboard as well as email so this solves my problem 100%.

https://addons.mozilla.org/en-US/firefox/addon/4437

No need to export anything.

Just save all the tabs in a folder (you already know how to do that), right click on folder, copy. Open notepad, paste. Voila. All URL's of bookmarks in that folder.