So far in the games/lore I believe we encounter
But I've been reading about the Xel'Naga and the species they tried to "uplift" before encountering the Protoss and later the Zerg. Are any of these species encountered in the games? I assume there must be non-sentient animals and stuff but are there other sentient beings or at least ones that are important somehow?
Given the events of the Heart of the Swarm campaign we now have new data to answer this question.
There would be three new important races to add there.
The Primal Zerg are introduced in Heart of the Swarm as the "Original Zergs" The ones the Xel'Naga uplifted, by taking their predatory instincts and introducing a Hive mind.
The Hybrids are a main plot point of SCII so far. They're meant to be a sort of "Fifth columnists" to start the darkness Amon is looking for.
And then we got the Shapeshifters...(WoL and HoTS spoiler below)
...whose only example right now is Samir Duran/Emil Narud, which served (past tense apparently) Amon "throughout the millennia".
There was a race of Ewok-like creatures on Endion. Technically, Earth Humans and Terrans have been evolving separately for so long that they are now separate species, with earth humans having much less genetic variation due to the United Powers League's policy of eugenics. There is a reference to a primitive alien race that the Protoss have chosen to protect and not interfere with due to something about their culture which the Protoss found impressive. It is not clear what this is. The protoss are said to be worshiped as gods on numerous worlds, implying that there are other sentient species. Finally, the saga has not actually left the Korpulu Sector, which is a relatively small portion of the galaxy. Given that it is generally assumed that the UED is more technologically advanced than the Dominion, it is conceivable that they have colonized and explored large portions of the galaxy with sentient species none of the others have encountered. Perhaps they are even at war with a few of them.
You forgot Duran, which don t seem to be a part of neither, but is trying to create the Xel'Naga again by hybridation between Protoss and Zerg.
You can also count the various neutral animals, but we don t know if the Xel naga saw them;
Information on the Xel'Naga are few, and only gave by Protoss and the Zerg Overmind, so while we know the great line, we will probably never heard of the details.
