What was the greatest invention since you were born?
The personal computer.
There are so many to choose from…
the remote control
surround sound
plasma tv
palm pilot
sanitary napkins with wings
SDMB? 
No, really the WWW.
I take some pride in inventing SEX. No, really!!!
Every car I’ve ever owned… (I’m a bit of a driving addict!)
Followed closely by the WWW (or, as I like to call it - the cyber sandbox)
E-mail.
But this is mostly because I really hate telephones.
Gotta be the home PC.
I’d also have to say the personal computer. Since this is probably going to be a common response, I’ll add that CDs and CD players are the among the greatest of inventions that have come along in my lifetime. They revolutionized the recording industry by improving the sound quality (record purists will disagree, though), eliminating tape noise, scratches and pops, “eaten” or worn tapes, eliminating the need to turn the recording medium over in the middle of play, allowing for instant random access to each track at the push of a button, and by being able to store over an hour’s worth of music. Plus, they’re smaller and easier to store.
What about inventions of vaccines? Jonas Salk invented the polio vaccine - before I was born, though.
Cordless phones and cellphones!
The answer has to be the intranet machine.
The intarweb machine of course. 
Television.
Peace,
mangeorge
Huh.
I thought this was going to be about the greatest invention that ‘you’ had made in your life.
In my case, that would be the cheese, marmite and treacle sandwich - far more impressive than it sounds, so don’t scoff, you!
To address the intended question though, the home computer would be up there, along with LCD technology generally, transplant surgery and maybe the Space Shuttle.
KY
I’ll second CDs.
The microchip. Without it, many other inventions (including the home PC) would not have seen the light of day.
“Scoff” ? I think you meant “Barf”. That sandwich must taste like the Devils arse…
As an employee of the largest Microchip manufacturer in the world my shameless plug is for - Wireless Data Transfer technology.
The photocopy machine that plugs directly into my brain.
Oh wait, I have invented that yet.
How long has central air conditioning been around? Because I think that may be the greatest thing ever…