Hi everyone! I'm glad to see this thread!
DD just turned 4. We are pretty much unschooling for preschool. We may start doing more formal school-y stuff when she gets to official kindy age (almost 2 years away, since she's a November birthday). She's pretty self-motivated at this point, and I don't go out of my way to do much more than provide learning opportunities and materials, such as workbooks, alphabet books, beads to count, computer games like Starfall when she requests them, etc. She hardly ever requests to do workbooks, but then some days she'll work in them for 20 minutes or so. We go on nature walks in the nearby woods most days, unless it's too yucky outside.
When/if we do something more formal eventually, I am leaning towards literature-based curriculum like Sonlight, just based on her personality. I bought a few of the books from the Sonlight P 4/5 list, and she loves them. She LOVES being read to, for as long as I will agree to it. She is also especially obsessed with story-telling, always requesting "Nice, sad, mean, scary, nice at the end" stories.

and she has recently started telling her own hilarious stories in exchange for the ones that all the adults in her life tell her.
When I feel like we're not doing enough formal stuff, she will let me work on writing letters and numbers with her. She can't read yet, other than a few sight words, but has taught herself to write most of her letters by copying from a Dora alphabet book with a magna-doodle attached (I didn't realize she could already write them until I started actually watching what she was doing with that magna-doodle). She loves painting, coloring and also playing with beans and similar sensory activities. Mostly she just does free play though.
I let her watch more DVDs than I would like to (usually 2-3 hours a day), but I tell myself that this is temporary, while baby brother is small, to keep her from interrupting his naps with the random exuberant yelling she does when she gets bored...
Sometimes she gets really into something, usually science-related- for example, at age 3, she got really obsessed with digestion and would watch a short online digestion video which ended in a cartoon man producing cartoon feces...

however lately she is just into being read to for her preferred activity. I guess she's kind of in a "taking it all in" phase...