If you want a structured curriculum, I like Abeka, but it's not free. You can also pick up little workbooks "curriculum" that say preschool or pre-k on the cover. You could go to the library and pick up a few things in the educational / school section on homeschool lessons. We like starfall.com to play together.
But what the others have mentioned is really how you "teach" preschool. I am way more anal than most, and thrive on lists and "stuff", so I made a couple lists that go like this every week: what do I want to do to meet his spiritual, emotional, mental, physical, social, (etc) needs? I'll think of something I'm going to do that focuses on these needs for the week and write it down. Then I make a list of what I want to teach. For my 5 year old (he'd be in pre-K because of his late birthday--he'll start K next year), it's like this: Math (he counts to 100 by 1s, 5s, and 10s, writing/recognizing numbers, greater than/less than games, very basic adding and subtracting games).
Reading, spelling, English (starfall.com is great for the beginning stuff, then we started getting little books that we read together, we have a "wall of words" for sight words where we made little bricks...as he learns a sight word we add a brick and we're "building" a house with them, we go through magazines or newspapers and he can highlight the words he reads without help, practicing the ch, oo, th, sh, ck sounds by sight and making stupid words with them that make him laugh: oo....add a p before, now add a p after, yay, it's poop! Stupid, but he's a 5 year old boy and he likes that kind of stuff, so we have to laugh, and he's learning to build words. I can say a word and he'll work at deconstructing it in his head and spelling it outloud while we're in the car. We sing goofy songs, when we first started we did watch The Letter Factory DVD. I don't know how old your child is, but if learning the alphabet, make letters with playdoh, paint and brush, color the shapes, finger paints, make them by lining up stones, writing in the mud with a stick, the alphabet train floor puzzle did more than anything on recognizing what letters go where in order. Playing simple games and little activities with you is important, and it is HOW they learn.
Another "class" is handwriting. We squish playdoh and play with it, I let him help me in the kitchen squishing meat to make meatballs, string beads to make bracelets or whatever, stuff like that--it's just quality time together BUT it is also great for building the muscles and dexterity in their little hands so they can write. Give them different things: chalk, markers, crayons, pencils, our dry erase markers and let them draw, ''write'', color, etc. Do little activities where you draw the line to connect one thing to another, or connect the dots with ABCs or 123s, simple mazes, etc. Joseph is now excellent at handwriting (in pre-K, he's writing as nice as my friend's 9 yr old son), and we make little cards or notes to give/send.
Computer time: he can play games on nick jr or starfall (I'm usually there to help him with instructions unless it's something he's an "expert" on). He also likes to go to youtube (with me there!) to watch entertaining or educational things. We use youtube to help us with little lessons on rhythm, basic music classes, origami, stuff like that.
Spanish: our family uses the Rosetta Stone homeschool edition and is learning Spanish TOGETHER. Art: we do different arts and crafts, the regular stuff as well as making puppets and putting on a show, or getting the free crafts that Lowes and Home Depot do one Saturday/month and doing that together, then taking them home and painting or decorating them with stickers. Music as I said before, we practice things we see on the internet, games too, and my 2 year old does a kindermusic program with me, I'll line up several pots and pans and give them wooden spoons, or we make our own "shakers" with formula tubes and rice, etc and put on a concernt. We take field trips to art galleries, museums, festivals that showcase art or music, concerts in the park, the symphony, we listen to EVERYTHING on youtube (classical, opera, doowop, pop, oldies, rock, country, raggae, etc). We sometimes take field trips to children's theater, the zoo, the aquarium, really ANYTHING that sounds remotely interesting we'll go visit. I remember loving Mr Rogers and seeing inside factories, so yes we've taken "field trips" to Mrs Bairds, a pizza shop, the local Dr Pepper factory, the Atlanta Coca Cola, etc.
For Health / PE we teach little health lessons on hygiene, teeth, food choices, exercise, etc. There's games in the backyard: soccer, Tball, dodgball, etc. My 5yr old does kung fu class 2 nights a week but practices EVERY DAY at home, he also does horseback riding lessons now (but in summer we'll stop horses and put both children in swim lessons). I let them lead me in stretches and basic exercises on the living room floor, we walk the dog, etc.
Geography, Social Studies, and Sciences? YES we teach those too. We have a USA map puzzle and we use it and practice learning capitals of the states and a little something about them as we learn them. He can tell us in order without looking the southernmost states from CA to SC because it's a trip we've taken and discuss a lot. He knows about deserts, plains, mountains, forests, beaches, islands, and peninsulas. We are learning about the Gullah community here, history about them, we visited a Gullah community center/museum and a restaurant, we listen to some traditional music, etc. We discuss social issues within the family and ways to volunteer on things we think are important. We had an AWESOME Civics lesson while voting in the primary, and right after MLK day too. We were able to tie some really neat things together. For Sciences: we play and explore (so much to learn from simple things like playing with magnets, watching leaves turn and fall, digging around in the yard, visiting the beach, etc). We also make "experiments'', made paper one day, use my microscope, do star gazing, etc. We also like to watch Sid the Science Kid and discuss what he's learning on the show that day.
We have prayer time and children's devotional time, we learn scriptures each week for Awanas, we include time for "Bible" class. We do "Home Economics" in a sense, because we clean the house and do chores, we cook together nearly every night now, I let them be involved in helping me do inventory, cutting coupons (I cut the ones I want, and they can cut the rest....because they don't cut straight enough yet but like to try), making a menu and shopping list, stuff like that. History comes up all the time in all kinds of ways.
We also go to events at the library (not just story time and crafts, but a magic show, or a drum circle, a story teller or a folk singer). I get books in the educational section for neat ideas or crafts. We take field trips or day trips. We talk, sing, and play. So you don't need a curriculum or special workbook you follow, you don't need it to even be an official "class time" either---just spending time with the knowledge that your child will absorb whatever you throw in the mix, and while I'm covering A LOT of subjects and my kids are incredibly well rounded, they don't really know it's a "class". When your daughter asks to "do something", ask her if she has an idea what she'd like to do. Does she want to role play, use scissors, have you read a book, dance together, or what? That could help if you knew what she was hoping for. If she just wants time with you and nothing specific, then soak that up and share with her.
