I'm reading Latour's book We have never been modern, but I can't imagine a single example of a hybrid thing. Can you name one?
In the context of Latour's work, a hybrid is something that combines aspects that would traditionally be considered to belong to the natural and social realms. For Latour, the distinguishing trait of modern societies is that they differentiate between nature and society, whereas premodern ones do not make this difference. Latour doesn't like this duality, and he defends that our culture needs to reconnect the natural and social aspects. A hybrid, then, is anything (a thought, a public issue such as global warming, a research project, anything) that successfully accomplishes this.
Latour's corpus of work has evolved through time. We Have Never Been Modern (WHNBM) illustrates his first foray into philosophy. That said, this book contains terminology that would continue throughout his corpus, and terms that would germinate into other concepts.
That said, a hybrid is--as has been correctly mentioned--some thing that represents the way social elements and natural elements mix and blend in the modern era. As you know from the text, Latour sees a 'proliferation of hybrids' as emblematic of the modern world. The irony of modernity, he notes, is that in the modern era we are so often seeking to continuously advance and reify the definitions and categories of the objects and concepts around us, that in seeking to increasingly become more modern we are in fact moving further and further away from a cohesive understanding of the world. Ergo, we have never been modern.
Hybrids are central to this thesis. And it's crucial to recognize that they illustrate an evolution of how Latour would come to crystallize the term actor in the approach called actor-network theory (ANT), with which he is most often associated. So hybrids are neither social nor natural, neither human nor nonhuman. Hybrids are connecting points for the ongoing, shifting networks of people and things that generate the modern world.
Importantly, hybrid is a term Latour would later largely leave behind. I believe this is because it is a term that also gets taken up in postcolonial studies, an area in which he started his career but left behind to focus on science. I also think he was uncomfortable with the term's connotation that there is some kind of seemless duality, instead of, as his work would later progress toward, multiple, shifting, overlapping, ongoing, mutable networks.
I think Allan M. did a wonderful job of explaning hybrids in the Latourian sense of the word. As to examples: Latour's first chapter's introduction is full of examples (from his newspaper):
"The smallest AIDS virus takes you from sex to the unconscious, then to Africa, tissue cultures, D N A and San Francisco, but the analysts, thinkers, journalists and decision-makers w i l l slice the delicate network traced by the virus for you into tidy compartments where you will find only science, only economy, only social phenomena, only local news, only sentiment, only sex. Press the most innocent aerosol button and you'll be heading for the Antarctic, and from there to the University of California at Irvine, the mountain ranges of Lyon, the chemistry of inert gases, and then maybe to the United Nations, but this fragile thread w i l l be broken into as many segments as there are pure disciplines. By all means, they seem to say, let us not mix up knowledge, interest, justice and power. Let us not mix up heaven and earth, the global stage and the local scene, the human and the nonhuman."
Latour, We Have Never been Modern, p.2/3
I have the feeling people asking for examples are understanding hybrids as objects, or 'things'. The whole point Latour is making is that hybrids are networks of actors (things, humans) processes, symbols, information, and that we got in swampy ground by trying to break these hybrids up in material and immaterial qualities, in science, etc.