Today's metro had a quick fact about which inventions people considered to be the greatest in the history of mankind. I don't intend to answer that, but still give my list of the greatest inventions, though not in any particular order.
Fire was listed as the number one invention in the questionnaire quoted. It is the start of an energy age, so it is important indeed. To my understanding, fire is the start of an age, when humans had other means of energy, but flesh, at their disposal. Wind and water mills, use of wind energy in sails, power plants using wood, coal, oil, and nuclear power are all just evolutionary steps after the great invention that energy can be used as a tool.
Which reminds us of the other great invention, lest we downplay the importance of something easily forgotten. The stick and the rock. Probably the first tools mankind ever used. They taught us that we can use things within the world to help us do our bidding. This is even more primary invention than fire and so often forgotten. Sticks and stones allowed us to use our own flesh, our own energy, in ways our bodies were never designed to be used in. Sticks and stones are the start of the age of technology.
Age of technology and energy brought many wonders to humankind. At some point humans found out that fire was not the only source of energy they could harness to their benefit. Animals and plants were domesticated for the benefit of society.
With the combination of technology and (relatively) abundant energy humans could produce more food than those doing the production and many people staked their claims for the surplus. Perhaps it is not surprising that warriors and priests (and of course, prostitutes) were the first ones to succeed. With their wake, or perhaps even before, came artisans and then merchants. Specialization started and it created trade and trade created money. The idea of having a common highly valuable material/thing that everybody would use as the medium for exchange revolutionarized trade and specialization. Salt and metal money could be divided into as small units as necessary and thus trade could happen whenever the buyer wanted the item bought more than the seller (and could afford it). Without money, trade would be rudimentary and could only happen when need is great, because most of the time the buyer would not have anything that the seller would particularly want. With money, human societies were transformed again, for better or worse, into an interconnected and interdependent web.
Then came the first true internet. Discovery of writing enabled people far apart both in distance and time to communicate (though not necessarily full-duplex). Modern inventions such as the phone, the computer, and the Internet are just evolutionary steps of making the age old web better, faster, and raising its storage and copy capabilities, and making the web more efficient.
After the creation of writing, it might be tempting to say nothing 'really new', nothing Big has been invented. Many of the modern inventions are clearly continuances of ages old processes and that is good. But are there others that would be important enough, big enough, and most importantly new enough to warrant in this list?