Who would you consider to be the most technologically advanced race's in Trek?

[WaveMan]

Ok discounting god-like beings (Q, Douwd, Cartaker[Nacene], Prophets/Pah-wraith etc) who do you consider to be the most advanced technologically?

I rank the Voth, Iconian's (with the toss up between these two as being representative of the most advanced) and Borg among the top advanced races, Federation after the 28th century are right up there and Krenim coming in at around equivalent to Federation levels in the 26th century. The Dominion was definitely advanced, probably ranking in at early 25th century Federation standard, The Tkon Empire would also have to rank among the highest technological societies though they are for all intents and purposes extinct (Portal 63 is still around though quiescent as of the 24th century)

The Caeliar would probably have to be close to being the most advanced, though they are non-canon and aren't mentioned in any TNG, Voyager or DS-9 episodes and only feature in novels.

As TTK pointed out the Cartaker[Nacene] aren't god-like, see post #4 below.
Any others?

[C5]

The Traveller's people (I don't remember if their name was mentioned, so maybe they already appear in your list) were fairly advanced as far as I remember. Then there are the El-Aurians, whose powers were very vaguely defined, but in her first encounter with Q Guinan seemed as if she had some way to counter him. I kinda like to consider both as the Trek equivalent to the Time Lords.

[The Tatterdemalion King]

The Nacene weren't godlike, they used all sorts of technology. In fact, their problem was an explicitly technological one.

[WaveMan]

The Nacene weren't godlike, they used all sorts of technology. In fact, their problem was an explicitly technological one.

true mate, I was a little zealous putting them in the God-like category, probably should include them in technological rating, and would be right up there, trans-locating ships 75000ly is pretty advanced. Thanks for the clarification.

[WaveMan]

Yeah the El'Aurian's ability's were left very vague, other then their ability to live a very long time (many centuries) and sense fluctuation in the time line. I don't know how Guinan would be able to counter Q's powers, it didn't seem consistent with what we saw of their race in the rest of the episodes. Plus you have the fact that most of the race were either destroyed or assimilated by the Borg (Guinan said the Borg destroyed their home world, and we saw many fleeing in Generation's), one would think if they were able to interact with Q on a one on one basis they would be able to resist the Borg.

[WaveMan]

they were simply known as the "travelers" from Tau Alpha C, apparently their racial name was unpronounceable by Humans. They were very much like the Time Lords.

http://en.memory-alpha.wikia.com/wiki/The_Traveler

[WaveMan]

I suppose you would have to add the Aldean's as well, though they had forgotten how to use most of their technology as of the 2360's.
http://en.memory-alpha.wikia.com/wiki/Aldea