ALTERNITY has a few of them. Some are in the Menace Manual, but I will give direct conversions.
Mechalus: you might want to ignore these, since they're very humanlike and require cybergear rules.
Sesheyans: my personal favorites, these aliens look like winged bat-salamanders with eight eyes. They have low-light vision and also light blindness (special sunglasses can remove the penalty.)
They can fly at 100 ft. (maneuverability is difficult to determine, but since they can hover it's good) - this alone gives them a level adjustment.
Their stats, directly converted, are quite harsh: Str +0, Dex +4, Con
-4, Int -2, Wis +4, Cha -2.
Maybe Dex +2, Con -2, Wis +2 is more appropriate...
They would get Zero-g training (as the feat) for free, since they came from a low-gravity environment - a small planet with very thick jungles.
Their history is pretty interesting: they were enslaved by a powerful human corporation and uplifted (against their will) to a high-tech existence from their stone-age existence. They adapt to tech as quickly as other races, however. Of course, some have escaped slavery, but most don't give up technology.
Before I spend too much time on the sesheyans:
Weren. Direct stat conversion: Str +6, Dex -2, Con +6, Int +0*, Wis -2, Cha -2. (Converting Int was difficult, it was either Int +0 or Int -2.)
They had really high durability (the equivalent of a massive Con +12 for D20 purposes) but it's probably not a good idea to use their inflated sttas.
Weren are about 7 feet tall and 450 pounds. Their height is within medium range but, like minotaurs, maybe they should be large.
Camouflage (Ex): a small +2 bonus to Hide. Their hair goes from black to white, but in all the pictures they have brown hair.
Claws: natural attack (use iterative rules) for 1d6 damage. Males have tusks as well, but using a bite attack is more trouble than it's worth.
Weren were discovered by a human religious organization, in a Rennaissance setting, and were a race of philospher-warriors who also carried muskets. However, they have trouble adapting to technology (additional -4 penalty) and so most resist using human tech.
Fraal are also called grey aliens. In ALTERNITY they were Medium-sized but in the Menace Manual they are Small. I prefer Medium.
Fraal had crazy stat bonuses: Str -4, Dex -2 (or no mod if you used Dark Matter), Con -4, Int +4, Wis +6, Cha +2. You probably don't want to use the direct stat conversions for fear of a weird level adjustment.
They also had bonus power points and could manifest
lesser mindlink at will and
suggestion three times per day. Roughly 1 in 5 fraal have levels in a psionic class and like to focus on Clairsentience, Psychokinesis and Telepathy (especially the latter). I suggest just using Wisdom for manifesting their powers (and coming up with a more balanced D20 Modern psionics system and advanced class).
The fraal don't know their own history; they lived in world ships for ~14,000 years, longer than even a fraal's lifespan, and came to Earth early in our history. They spent a lot of time watching, but
some spent their time experimenting on Earth life, like cattle or humans.
Their tech is more advanced than that of humans, although they're not warriors.
The t'sa are a dizzyingly fast race of small reptilians (probably Medium, but definitely shorter than a human). Stats Str -2 (I think), Dex +6, Con -4, Int +4, Wis -2, Cha +0. Again, modify as appropriate. Also they have natural armor +6 (again, modify as appropriate).
They had a bonus to Initiative (probably +2) in addition to everything else.
I don't know much about t'sa history. They are fiercely independent and won't allow the humans to dominate them. Although high-tech, they had not discovered faster-than-light travel when they met humanity... but they very quickly learned it and developed their own space fleets.
A lot of Dark Matter races were copies of these races. Sasquatch were basically Weren but with a different history (lower-tech, replace human with frrall in their history). In Menace Manual they're the same thing... but use the Dark Matter history.
Sesheyans became mothmen (same balance, different flavor), fraal became greys (got Dex +0 but otherwise were the same), t'sa became kinori and the mechalus became sandmen with some slight stat mods.