Speculation on possibilities taken from the pages of the Core Rulebook (take this with a grain of salt):

Edit: Sorry for the Length

The Sun:

Whale-like fire elementals

plasma oozes

Jungle box sentient plant monsters

the "deep cultures" of the sun

Aballon:

other Aballonian constructs

Castrovel:

Lashunta

other varieties of Formian

Sky Fishers (already in AP)

Akiton:

trash-eating Kheftaks (similar to Otyughs?)

tusk-winged Noraska

Ysoki

ghostly creatures called Khulan

winged creatures from Qidel

Diaspora:

"Diaspora Wyrms"

Twisted figures in yellow rags (from the House of the Void)

Eox:

Glass Serpents

Semi-intelligent grub-swarms

variety of undead

Elebrians (already in AP)

Triaxus:

(note to self, look at Pathfinder sources for ideas)

Liavara (and Moons):

Air Plants

Giant Bacteria

Keji Swarms

Tarenake

Predators (vampiric tentacles, magical fields, acid-coated web-nets. suggested to be separate beings)

Dreamers (variation of Barathu)

sentient arthropods

Philosopher worms

mortal incarnation of Hylax

Lights of Hallas (already in Alien Archives 1)

Bretheda (and moons):

Barathu (Alien Archives 1, although variations would be appreciated)

living tools/tailored viruses/semi-intelligent servitor races (created by Barathu)

Confluence

Kalo, Maraquoi, and Urogs (all in Alien Archives)

Apostae:

Ilee (survivals from a past age?)

Drow (Alien Archives)

Fleshwarps (augmentation sold by Drow)

Aucturn:

Great Old Ones (possibly itself, at some point)

Elder Mythos/Old Cults (Great Old Ones, Outer Gods, any number of spawned races, and races dedicated to the worship of the Great Old Ones)

Dominion of the Black

Nyarlathotep, incarnate as the Black Pharaoh

Carsai the King

inhabitants of the pre-gap warships/madness-inducing hulks in the atmosphere

Orocorans (Alien Archives 1/First Contact)

the Midwives

Aucturn's child, Great Old One

Arquand:

long-necked, six-legged antelopes

four-winged birds

Azlanti Star Empire:

inhabitants of Thenekral

17 officially designated "sentient alien species"

Neskinti

Vilderaro

Daegox 4:

the Daegox (possible name for the humanoid race that rules the Daegox Corporation and Daegox 4)

Daimalko:

Daimalkans

Empyreal Lord, Duellona

Colossi

Kaiju

Volkarians

Ykarthans

skinless, eyeless creatures

Embroi:

mask-faced Embri

Levaloch devils

Occhiorasoi (Malebranche)

Jedarat:

microbial mats

Lothun:

(Inhabitants not described in Core Rulebook)

Orikolai:

Hashukayaks

Hub Geese

Orry:

Orrians

Preluria:

Psychic Gas Oozes

Vorlath

Xystrian Brotherhood

Riven Shroud:

Aatevak

Qotraua

Xixinnt

Shadari Confederacy:

numerous races including:

Draeliks (Alien Archives 1)

Sceaduinar

Skrell

Balrodds

Aeon, The Unmaker

Tabori Cluster:

Unmentioned

Veskarium:

the Vesk

cave-dwelling snake-people

jackal-faced arthropods

stranger creatures

squid folk of Vesk-2

ant like beings of Vesk-5

feline humanoid barbarians of Vesk-6

pacifist Frost Behemoths of Vesk-7 and Vesk-8

Cult of the Devourer:

Atrocites (AP)

Dominion of the Black:

Infinity-Ceases-Now

The-Five-Who-Speak-As-One

The-Whispers-of-the-Void-Have-Eyes

Dominion Starships

Shipminds

dozens of races

Swarm:

Swarm

Shirren

The Unseen:

formless, ethereal refugees

shape-shifting drones of inter dimensional brood-mothers

manipulators of interstellar commerce clad in convincing skin suits

Reptoid

fungal parasites

Grays (Alien Archives 1)

(potentially aligned with Shadari,as reptoid opened a weapons vault to Shadari Pirates)

other races:

Androids

Kasathas