The best hunting technology advancement I can think of is very revolutionary. It didn't exist 15 years ago and most people didn't hear of it 8 years ago....

... The Internet. (hunting forums and websites)

I've learned a lot about the outdoors by being there and watching. I've heard countless stories and articles about the outdoors.
But in this forum, for example, I have near real time interaction with experts from all over the world to learn from.

When I started bowhunting, I knew nothing really. None of my family hunts nor any of my friends (at the time.) So I didn't have anyone to fill in the vast gaps in my knowledge or show me how to do things. I tried joining an archery club but the fellas were to interested in looking macho or making a sale to teach me anything.

The Internet - 100% hands down - the best advance in hunting especially HNI

Guess I should have read all the way to the bottom before posting - MattPA already had my answer lol.

about the only thing I visit more than the forums here is MyTopo.com!

i would have to say...

treestands(summits)
fiber optic sights
releases(even though i don't use one )
carbon arrows
practice targets
cell phones
the internet

and i'm sure i can think of some others