About the Borg Species List
 This list was originally compiled by Neo Matrix and updated with
information from Starfleet
Headquarters, Delta
Blues, and M. Meneks of BorgSpace.  See also the StarTrek.com
Library, which was pointed out to me more recently.
 I'm trying to keep it up to date, so please email me if you know
of a species I've missed or a source for one I have.  I'd particularly
like corroborating evidence for Species 2461, or at least a witness
who heard the species numbered.  Many thanks to all those who have
already mailed in corrections and additions.
The List
And the assimilated are:
- Species 116: Arturis' people, a highly intelligent race
    that fought the Borg for centuries and invented a quantum
    slipstream drive.  "Hope and Fear" [VOY]
 - Species 125: The original species of the Borg
    Queen. "Dark Frontier" [VOY]
 - Species 149:  A species with advanced medical knowledge.
    The Borg assimilated them and nanoprobe technology to 
    reverse cellular necrosis.  "Mortal Coil" [VOY]
 - Species 180: Ferengi.  "Infinite Regress" [VOY]
 - Species 218: Talaxians - 39 of them were found on a small
    freighter in the Dalmine sector.  "The Raven" [VOY]
 - Species 259: A species that inhabited Galactic Cluster 3 (a
    transmaterial energy plane, intersecting 22 billion omnicordial
    life-forms).  The Borg assimilated their autonomous regeneration
    sequencer technology.   "The Gift" [VOY]
 - Species 262: A primitive culture whose mythology included
    the Omega Molecule, a substance that could burn the sky.
    The first of 13 species familiar with Omega, all assimilated over
    the course of many years, beginning 229 years before Voyager's
    time.     "The Omega Directive" [VOY] 
 - Species 263: A primitive culture who believed that the
    Omega Molecule was a drop of blood from their creators. "The
    Omega Directive" [VOY] 
 - Species 312: Unnamed species who had technology similar to
    the shielding that hid the Ventu.  They may have been the species
    who erected that shield. "Natural Law" [VOY]
 - Species 329:  The Kazon.  The Borg encountered a small
    colony of them in the Gan sector (Grid 6920) but 'they were
    unworthy of assimilation.' "Mortal Coil" [VOY]  
 - Species 521: Chevullians.  (Jim spells them Shivolian.)  A
    reptillian species Voyager encountered on the Markonian station.
    "Survival Instinct" [VOY]
 - Species 571: Humanoid.  The original species of P'Chan,
    the drone formerly known as 4 of 9.  (Yes, that's 9 as in 7 of 9.)
    "Survival Instinct" [VOY]
 - Species 689: Norcadians.  Mezoti's species. "Ashes to
    Ashes" [VOY] 
    
 - Species 2461: The Brunali. Icheb's species.  They infected
    the Borg with a pathogen by sacrificing one of their own children.
    [Startrek.com lists this species, but I've been unable to confirm
    that the number was actually mentioned in the episode cited.]
    "Child's Play" [VOY]
 - Species 3259: The Vulcans.  "The Raven" [VOY]
 - Species 4228: Hazari. "Technologically advanced, extremely
    violent. They make excellent tactical drones."  
    "Think Tank" [VOY] 
 - Species 5174: The Borg found a small ship of this species.
    They had been sliced and diced by Hirogen hunters. "Hunters"
    [VOY] 
 - Species 5618:  Humans. Origin: Grid
    325. Warp-capable. Technologically limited. "Dark Frontier"
    [VOY]
 - Species 5973: A non-corporeal, multi-spectrum particle
    lifeform the Borg encountered in galactic cluster eight.
    "The Haunting of Deck Twelve" [VOY]
    
 - Species 6291:  The Yridians.  Everyone, even the Borg,
    thought they were extinct, but Captain Ransom of the Equinox
    proved otherwise by making first contact with them in his days
    as an exo-biologist. "Equinox (Part I)" [VOY]
 - Species 6339: "Humanoid. Warp-capable. Origin: Grid 124,
    Octant 22 Theta. They first encountered the Borg approximately
    four years ago. Since that time, 11 billion individuals have been
    assimilated."  They were trying to infect the Borg with a virus
    and they got Seven instead.  "Infinite Regress" [VOY]
 - Species 6961:  The Ktarians. "Dark Frontier" [VOY]
 - Species 8472: They Came From Fluidic Space!  They had the
    honor of being The Species That Ate Borg for Breakfast, until
    Janeway came along to defend her Cheerios. "Scorpion" [VOY]
 - Species 10026: Just a few people in the wrong place (Grid
    532) at the wrong time (circa Stardate 52619.2).  The Borg Queen
    assimilated all of them (392,000) to make a point to Seven.
    "Dark Frontier" [VOY]