I think I’d show them the freaking Starbucks on every freaking corner. They’d wonder when did overpriced coffee become the national religion.
I’m not taking you to the future, then. You’re no fun at all.
My first thought was show them the Phantom Menace without mentioning anything about ESB or RotJ …
DVDs would be pretty impressive, CDs not so much, cos you were used to music on discs in the 70s, but watching movies on a disc?! Woah
I seem to remember seeing a huge LP-sized laser video disk either in the late 70s or very early 80s. It was at a car dealership, and the machine to play it probably cost as much as one of the cars.
I would use my webcam and have a real-time “face-to-face” conversation with a friend in Tokyo. 'Cause that’s the shit I thought was “science fiction” when I was a kid in the 1970s. Likewise my cellphone that flips open like Captain Kirk’s communicator.
I don’t think this is true. I was playing with TRS-80s in 1978 - I was living in the middle of nowhere in a small town, but our school system still had a few computers for the elementary school kids to play with. The Apple II came out in 1977, and they wasn’t uncommon by the late 70s to see them around.
I’m not saying they were ubiquitous, but I don’t think they were “exceedingly unusual” either. I was begging my parents for a computer long before 1980 hit. And a modem, too.
Personal computers were known of, but they were an incredibly expensive luxury. Affordability and accessibility came in the 80s, helped along by Commodore, Atari, and Sinclair et al, and that’s when things started to move.
The point of surprising someone from the past isn’t to show them something completely unknown, but to show them something so much cooler than they would have imagined, especially with such a short period of time having passed.
I was in college in the early 80’s, and we were still using punch cards to analyze research data. We got an Apple II+ in about 1983 and felt like we were on the cutting edge of technology. PC’s were certainly not common in the 70’s, at least where I was, and connection to the internet didn’t become common until much later.
My aunt had a story of working as a secretary/typist for a major Sydney law firm in the 1970s. They had bought themselves a newfangled “word processor” that could show ONE LINE of luminous type at a time. They used it for record keeping, but my aunt was obliged to re-type in paper everything she had entered into the word processor, because the firm’s partners didn’t trust it.
Someone in my age group? I’d show them Assassin’s Creed or Beautiful Katamari or something on the X-box 360. Because the graphics in Space Invaders were so awesome. Then I’d show them the iPod. Walkmans weren’t quite around yet back then, were they? I’d show them something on an HDTV (I think '78 might have been the year my family got a color TV? Later than that?).
Then I’d have them pop back home for a minute and bring back 10 Millennium Falcon toys in the original box with the little gun pieces and we’d retire.
No, nobody was using GPS in 1978.
While the first experimental GPS satellite was launched in 1978, the system was not operational until late 1993.
See here for a timeline.
I know this is true, because I was in the Navy at the time, and was amazed when we got our first military receiver around this time.
We’d been hearing about the system for 2-3 years at that point, though it was referred to by its official name, NAVSTAR.
Show them who the frontrunners are in the US presidential race.
Heh. AT&T showed off picturephones at the 1964 World’s Fair in New York. I got to use one. They had flopped once already by 1978.
Heh…wow. You know, before today, I’d never even HEARD of the PLATO system.
That’s fairly impressive to me, in 2008, in it’s own charming way. Like a living slice of transistorpunk! 
Fine. Some like nookie & some like Wookie. To each his/her own.
And Dammit Rockford, get a voicemail, will ya…!?
You know I love that organic cooking,
I always ask for more.
And they call me Mr. Natural,
On down to the health food store.
– Junk Food Junkie, released 1976
<back to the future>Ronald Regan is president?!</back to the future>
Oooo, not around here you wouldn’t have! 
Well, I’m not going to get into the technology one-upmanship seen in the thread above, but I do see that Laserdiscs debuted in 1978, so I don’t think my memory is utterly faulty.
Has life expectancy increased significantly since 1978?
I take them to a strip club. Not because they need to go, but because I WANT to go.