Cindy. For me, the most useful invention of all time is surely the Internet. We can now reach people and do business faster. I own a clothing store in Mexico city,and there's a lot of competition. I also have a website. Now, people from all over the world can buy my clothing. With emails,I can keep in touch with friends and family in mexico and around the world. It's faster than usual mail,and it's cheaper than using the phone!