Potentially the most important could be the Tollan... their technology is exceptionally advanced: communications, walking through walls stuff, ion cannon, weapon disabling beams, Goa'uld control vest thingies etc. Oh yes - and building their own gate!! :alienooh:
We may assume that this is also not the peak, but a general selection of their knowledge. So if they were actually pushed into a corner they would presumably be able to come up with some REALLY advanced stuff.
Or, perhaps they will actually turn out to be either the Furlings or Ancients, or fairly directly related - they seem leaps ahead of Goa'uld, since they can actually develop, where the Goa'uld basically just nick it all.
However, I agree with other posts: the Tau'ri are the basis for pretty much the majority of Goa'uld seeded/terraformed planets in the nearby galaxy: and hence or otherwise provide the Goa'uld with servants, Jaffa and hosts. We are also becoming a nuisance to them on a number of of occassions: including the deaths of at least three system lords (and a fourth who was later revived). If they are following classical Egyptology, there are only 9 "gods" in the Ennead - so keep going and we should dominate by the end of series 6 or 7!!
The Nox so far are staying neutral, whilst the Asguard are almost a galactic police-force. Every assumes they have the power to stamp, so everyone is basically nice to them and behaves in a polite manner.
So - despite being technically perhaps the weakest race, and coming from a single planet with arrogance and naivety, we seem to be kicking butt! :evil: