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inexpensive, dependable, universally available birth control for everyone.
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a global Bill of Rights that protects all humans.
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inexpensive, dependable thermal depolymerization.
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a global cultural shift to acknowledge and repair our detrimental effects on the environment, including global climate change.
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stem cell therapy that includes tailored organ creation.
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cloning and recreation of extinct species such as the Carolina parakeet, thylacine, and mammoth/mastodon.
Just the usual.
World peace.
An end to hunger and poverty.
Jet packs.
Holodecks.
Transporter rooms (and they have to make a cool sci-fi swooshy noise when they slide the controller thingy).
Universal free access to the Straight Dope, running on the fastest, most reliable and powerful servers in the world.
3D television (this one is really overdue).
Space tourism. Like, to Saturn’s rings and stuff.
Discovery of a cheap, clean source of more or less limitless fuel.
Painless, non-invasive cures for all ailments and diseases. Preferably using something that looks like a sci-fi version of a magic wand.
The ‘eat whatever the hell you want, it makes no difference’ magic slimming/weight control pill.
Beatles reunion.
Downloadable brain feeds. Want to learn Italian? Click, whirr, click… you now know Italian.
Droids. Just smart and powerful enough to be perfect slaves. Not quite smart and powerful enough to take over the world.
The end of religion, through universal lack of interest.
Chocolate that makes you fitter, stronger and healthier.
Ray guns that fire bright ruby-red rays, and only I can say who can have them.
Light sabres. Or just one light sabre, for me.
An end to ‘celebrity culture’ and a return to valuing people for what they actually contribute, i.e. a society that is more interested in nurses than idle heiresses.
That’s enough to be going on with. And the 3D telly really ought to be here by now.
Cloning of extinct species, from the mundane (the dodo, thylacine) to the awesome (mastodon, dinosaurs).
Consumer Virtual Reality/VR implementation in everything from games to the net to work. VR should be as monumental and transformative technology as the telephone was.
All my best answers to this question are proprietary.
Here’s one I’ll donate to the public domain: A “Love Boat”-themed casino on the Las Vegas strip (using the actual ship).
I’m still waiting for Dick Tracy’s 2-way wrist TV.
Screw smartcars and jetpacks. I want to be able to wake up, press a button, and *beam * to work. And I’d like to arrive there showered, with full makeup and good hair, and a different outfit every day.
Oh, and world peace.
Hasn’t it occurred to anyone that sexbots are the cure for AIDS? That disease would disappear in a single generation if we all switched to a daily regimen of robosex. That is, of course, unless people were sharing sexbots with multiple partners and not putting them through a wash cycle between uses. Come on, people, all you have to do is press the wash cycle button when you’re done.
I would like to see a cure for cancer and dumbness.
Cuba’s government to change to a democratic model, that does not suppress dissenting ideas, political, or personal expression.
Neuromancer-type technology. I’d be first in line to have a microchip implanted in my brain (providing it isn’t wintel - how would you ctrl-alt-del an implant?)
Telescoping thigh bone implants. Long legs are okay most of the time. However, I’d love to be able to sit in a ballpark, theater, or airplane without having my knees pressed against the back of another seat.
An end to homelessness in our country.
Acceptance of gay marriage.
An AIDS cure.
A Cancer cure.
Brett Favre to win another Super Bowl.
That’s the one. Sorry I’ve had a very bad lingering cold the last few days.
Oh and while I’m on the subject-a cure for the common cold… 
Hell, I’d like to see the Heat Death of the Universe.
A single world government – run by the Swedes!
Eternal youth and an end to disease through nanobots.
100%-efficient solar cells; limitless free energy.
A way to directly edit your own personality.
The entire contents of the Library of Congress in a PDA the size of a paperback.
Well, if I may be a wet blanket, from what I’ve read, the closest discovered planet is ten light years away, and is a gas giant. So if we find an “M Class” planet, what with the cosmic ray problem, it will be basically impossible to get to.
The thing that lept to my mind was the idea of solar panels that are just spooled out of manufacturing machines, making it practical to plaster every Sun Belt roof and southern wall with them. What if the daytime demand was reduced by half or something on sunny days?
Medical science curing death.
As a Swede, I must ask- Huh?
Oh, and I second the Neuromancer technology, I’d stuff my head full with every implant I could get my hands on! 
Also, an end to all Abrahameic (SP?) religions would be neat.
Not only has Sweden done the best of all nations in ensuring a decent standard of living for its working classes, the country is remarkably clean, well-run, orderly and efficient. (I visited Stockholm for two weeks last September.) If all the peoples of the world were to adopt the Swedish mindset and values, the planet would be a much better place.
Sounds good on paper, but it would be absolutely wretched to have to deal with.
Okay. I’ll narrow it down to curing MY death. 
(Although there may be some who try to tell you that would be wretched to deal with, also.)