When I was in high school psychology class, of course we learned all the fun stuff about what Freud proposed. You may remember his division of the psyche into the id that acted on the 'pleasure principle', the superego as the voice of society/parents, and the ego as the moderator and 'self'.
During a conversation with a friend of mine, he said he particularly remembered what we learned about Freud's psychosexual theory of development. Basically that people are "polymorphously perverse" from birth, and we derive sexual pleasure through a series of phases: the oral phase when breastfeeding, the anal phase when potty training, the 'latent' phase when we suppress all of it, and the 'genital' phase where... well, that should be obvious to anyone over the age of 10. And we learned all of that fun stuff about how dreams are a window into the subconscious mind, where trees represented penises and doorways represented vaginas.
Not until college did anyone bother to tell me Freud's real claim to fame: popularizing the idea of the subconsious throughout the Western world.
Up until that point, most popular discourse about minds and wills and people assumed that we were basically rational beings, our decisions made consciously and with premeditation. Hell, a lot of economics today still holds on to those assumptions (with some good reason, as spending money is something that people usually give more thought to than other decisions).
We know now, partially because of Freud, that this isn't true. People do a lot of things without much thought. A lot.
Talking is one of my favorite examples of this. Neurotypical people do not pause and think and put together a sentence before opening their mouths. We hear or see (or smell or taste or feel) something, and with maybe a second's pause we open our mouths and out come our thoughts! In that second before we open our mouths, we may decide not to share our thoughts and instead 'keep them on the inside'. But we don't usually consciously pick out our thoughts, or the structure of our thoughts. They just happen.
An even better example (and one Freud would approve of) is fear. I am afraid of the dark; I'll admit it. I did not sit back and think, "When it is dark, I am less likely to see things around me and thus more vulnerable to certain harmful things, and so I shall avoid the dark." Instead, I simply get creepy feelings whenever the lights are out. I have seen a lot of crime shows and horror movies that usually take place in the dark, and so I hypothesize that subconsciously, without any intent, I have associated darkness with unpleasant things. (And given my night-owl circadian rhythm, this is a giant pain in my ass sometimes.)
How about food preferences? Besides the things that most every omnivorous creature likes (ice cream on a hot day, greasy fried foods, sweet fruits, savory sauces), I mean. For example, I like broccoli. I did not sit back and say, "Broccoli is a nutritious food, and so I shall incorporate it into my diet." It's just damned tasty to me. Or tomatoes. I freakin' hate tomatoes except in very select circumstances. I can't eat them. I just know it has something to do with being forced to eat a tomato when I was a very young child. Just thinking about it makes me get all squicky inside.
If you mull for a while, you can come up with a whole long list of things we do or feel without conscious thought. But none of this was part of the greater dialogue about How Man Works until Freud came along and suggested that maybe things happen in our minds that "I" isn't aware of, and it's a normal part of human functioning. And now that we know that certain things aren't conscious, we can start learning what does cause and affect these things. And for that Freud should be remembered as long as society lasts.
Of course, the guy also gets mondo cool points for his given first name being Shlomo. Hell yeah. ;)