Pencil and paper. It was tough chiseling all of my homework in stone tablets.
GPS Navigation. I don't mind pulling out a giant map on the side of the road during long trips on the road but... Yeah I do.
Oh also Yelp!
I'd go for "Internet"
I know many would think about negative sides of this subject which impacted every society on this planet at some point, i'm aware of those, but whoever which exposed to the negativity are entitled to their own fault. For me, this is a greatest thing in the world as it made my life a thousand times easier. Plus, we are all here and communicating and discussing different matters, telling stories and sharing experiences and venting and sharing emotions, all from different spots of this world. It's only because of the network.
Also i would point out many high medical technologies which caused many people survive from the diseases which took lives in previous ages. I wish there could be more technologies before so they could have better chances surviving.
I wish I had my grandson about 10 years earlier so I could do more things with him. But my son was a little slow ... LOL
Nothing ... There's "too much stuff " now ... I want things to be more simple cos I do ... Less stuff.
Our knowledge of the genetic code by about 20 years earlier . . . By now we would be a lot further in applying that knowledge to some of the nasty diseases that still plague us.