Hi guys, I'm new here and I only play diety with raging hordes. The worst wonder's to me are SETI Program and Darwin's Voyage, Great Library, and Oracle, Apollo Program, Manhattan Project, Tzu Su's War academy.
SETI Program comes too late in the game to be of any real use, and if you've been building caravans and setting up trade routes and government is democracy you should already be rattling off discoveries every 4-5 turns.
Darwin's Voyage and result in as few as 1 free discovery because if you've researched and are extremely close to getting a tech when you finish DV then you just get a tech you almost had in any case +1 additional tech... not worth the effort whatsoever. Besides, if you know what you're doing you should be way ahead in terms of tech, and also pushing frieght all over the map allowing you to knock off discoveries really quickly, so this blows to me.
Great Library is useless. If you've got Marco Polo's Embassy and are trading techs with all the other civs you'll quickly be way ahead in techs and have no need for this at all, in fact the GL backfires on you because you'll be way ahead and tech and have nobody to trade with, which means all the civs turning on you even faster.
Oracle just doesn't last long enough and expires with Theology which is a tech you're going to want ASAP.
I also think Apollo program is one of the horsehockytier wonders. Someone's going to build it eventually and it doesn't help in the space race that it was you, so why was all the production that you could be putting towards something else? I usually just build this out of pride, can't have the computer building it first.
Manhatten project for all the reasons that everyone else has stated.
Tzu Su's War academy is totally useless for me because I never try to win with military, I much prefer to explore, colonize, trade and get techs.
To that end the essential wonders are Macro Polo's Embassy, Pyramids, Michael Angelo's Cathedral, Hoover Dam, United Nations... and yes... Effel tower!
Even though everyone seems to hate the effel tower once your've colonized tonnes of the map and are way ahead in techs all the computer players will unite in hatred towards you. Having the UN doesn't help when they just refuse to talk to you anways and it's one of the cheaper wonders, so I say go for it.
Anways, just my two cents.