dd (almost 3) loves starfall.com (if you haven't seen it, it's a learning ABCs/learning to read site with a lot of cool stuff). I think it is very possible to get "academics" in at this age in a fun and playful way. I don't see play centered on learning letter sounds, or how to count, etc. as being fundamentally different than other play - every game or toy teaches something and it's our culture that marks out certain information as "special". So I would go ahead and introduce these things if you are so inclined, just don't make it a chore.
I don't use a curriculum, but there are several things I do with dd. The most important is just to read a lot of books - I try to read at least 5 a day (more if she asks). Our collection of books contains many which have "educational" value, such as books about animals and nature (we especially like the "Smithsonian's Backyard" series), or books showing other cultures and times; and of course we have a few abc and counting books.
Weather permitting, we go outside and look at plants and other wildlife, and identify and talk about them. You could view this as a sort of science curriculum, though it isn't really any different than what most parents would do naturally when outdoors with their child.
We recently introduced "geography", by which I mean we have an inflatable globe of the world, and when we see a mention of a place in a book I get the ball and point it out (e.g. "Zebras live in Africa... look, here's Africa!). She may not get the abstract concept, but by the time she does she'll know where a lot of things are. And what animals live there. dd enjoys this and will even bring me the globe and ask me to identify places.
For "math" I just take opportunities to count things, and occasionally read a counting book (we really like "Counting on Calico" because it has cute cats and goes all the way to 20).
For reading I take several approaches. We go to starfall.com, we read abc books, occasionally I will sound out a word when reading or point out short sight words. Sometimes when we are drawing or painting I write words - I take requests, and dd loves seeing her own name and our pets' names. We also have a set of magnetic wooden letters to play with. I don't do all of these things every day, I just try to pick the one or two that she is most interested in (and she often initiates these activities, especially starfall).
I also think it's important to involve her in what I do. She can learn a lot by helping to bake or clean.
I hope this post was helpful and not overly long! How to handle the preschool years seems to be a very individual thing, and how people think about what they are doing even more so (e.g. my "science' is someone else's "playing outside"). In the end you just have to go with your gut about what will work for you and your dc.