Let’s see:
A licensed DVD player for Linux.
A Peer-to-peer system actually approved by the media industries.
A computer with 6000mhz, 128-bit chip that uses a whole new platform entirely. Non-x86, Non-pentium class or compatible, non-Motorola 68000, non-Commodore even. Of course no current program can run this new baby. Besides, they are going along with the idea of stringing many old CPU’s together.
Automatic cars! At least, cars that can be switched to auto-pilot on specially equipped highways. Not a huge technological problem, it’s mostly the legal and liability issues that are holding it back.
Velomobiles - i.e. human-powered cars with enclosed cabins. There are some already, like the Leitra, but the high cost ($5000 for the Leitra) make them unpopular. Mass production would reduce that cost by an order of magnitude.
Computers that don’t crash. It’d be expensive but it could happen if consumers demanded it. Instead consumers prefer buggy but feature-rich products.
I can’t believe no one has said this: Sexbots. That’s right sexbots. I’m not talking about those hokey pokey plug-in vaginas they sell at the local porno shop. I’m talking a sexbot that’ll be better than the real thing. I think it’d change the world more then the internet, or steel. Think about it.
Apparently you’ve never seen the Real Doll site.
I’ve been dying for this one -
reliable traffic sensors. The kind that at 2am, realize that no one is coming from the other direction & turn the traffic light facing me green.
Okay, let’s see:
they should put huge rubber rings round cars (either inflatable or very soft rubber) like the dodgems/ bumper cars at fairgrounds. They wouldn’t be very aerodynamic or look very good but no one would die in a car crash ever again. In fact we’d deliberately crash cars into each other because it would be such good fun - they’s just bounce off each other and off walls or whatever.
beer glasses that are as big as buckets so you don’t have to keep getting up and going to bar every 5 minutes.
conveyor belts on pavements/sidewalks so you don’t have to walk anywhere.
an escalator that goes all the way up to the moon.
I’ve always wanted a tail-that would fucking rock.
A commander’s chair like Capt. Kirk in Star Trek, only one that would operate the TV and the Internet Access (especially if the keyboard was split: one half on the left arm, one half on the right).
With a kick-ass foot rest and recliner action.
ya know, now that you point it out, I’d hate to have a bathtub with indigestion. Peristalsis does run in reverse, you know.
**
that is the most squickful thing I have ever heard since that time my cousin jake snuck into his dad’s butcher shop, dropped acid and… well, no point in telling that story again.
An Orion type nuclear starship. I agree with Carl Sagan, it’s about the only good use of nuclear weapons I can think of.
Oh no! WHAT happened-now you MUST tell that story!
A toilet with automatic ass wiper.
Finger print recognition car starter.
Fat burning pill that really works.
A cell phone chip that you can implant directly into your cranium.
robotic vaccumm cleaner
cars with biult in aircompressers so you don’t have to go to the gas station to fill your tires/ or fix a flat.
tuper-ware with built in microwave.(forgive speeling)
A SDMB with built in spell checker.
I’m sure I’ve seen this on Lexx. 
Home electric fans made to last more than 18 months.
All the foods you used to like but that aren’t made anymore. Dammit, I want my Peanut Butter Buffalos! (obscure '70s toaster pastry.)
$1200 hummers
PLEASE won’t somebody invent this–the market would be tremendous!!
Pacifiers with locator devices–you could clap or whistle and it would beep so that you could find the damn thing.
Those of you who can’t understand the logic of such a thing have never had a kid who just won’t sleep without his binky! 
while we’re in that department:
A surefire cure for colic.
I’ve always sworn that there’s a Nobel prize in it for the inventor (as well as untold millions). Like in the above post, if you haven’t been there, there’s no use trying to explain it.
but now we’re off topic, which is “stuff they Could make…”
I’m sure that if someone could make that, they would have.