A Vulcan Philosopher named T'Uerell who was obssessed with "logic" and "perfection" was credited as the creator of the Borg in the videogame Star Trek: Legacy. I was wondering if she ever appeared anywhere else as she was very badass.
A later origin was discovered by the Vulcan scientist T'Uerell during her attempt to become the new controlling entity within the Collective in order to mold the galaxy into a realm of pure logic. After entering a deep meditative state, she mind melded with the Borg Collective consciousness and discovered that the origin of the Collective lies with the human-built machine probe that would be known as "V'Ger."
As regards further appearances of T'Uerell in the Star Trek EU, there haven't been any.
They did at least leave the door open for a possible sequel though...