Well I'm in the same boat, sorta. I'm set to start preschool with DS this fall (he'll turn 4 in October) and I wish someone could just slap a curriculum in front of me and tell me to follow the directions.

I spent 2 hours with my eyes bugging out at a local teacher's supply/curriculum store before coming home last year near in tears. In desperation, I sought my MIL's help, as she successfully homeschooled 4 children. She told me to relax, and just do educational play, life skills and interactive learning until he was around 4 (this Fall). So, I'd have DS count things at the grocery store, or separate his car collection based on colors, types, sizes, etc. We played "which is different" with his toys. I taught him colors, shapes, opposites (big/small, high/low, loud/quiet), same/different, numbers, alphabet. What tv he does watch is on the educational side (Dora, Sesame Street).
If you're looking for a preprinted set curriculum, there are plenty online you can order or get books. Here are a couple websites that are great if you want to do it on your own or supplement some book curriculum.
Valuable Preschool Years - Fun Preschool Curriculum
The Perpetual Preschool (even has some great toddler things!)
Learn to Read at Starfall - teaching comprehension and phonics (DS loves this!)
Brightly Beaming Resources
If I come across more, I'll post them for you. I think the biggest thing is just being involved in your child's learning and teaching them not only letters, numbers and the like, but skills for life (manners, cause/effect, communication, etc).