I have one favorite Preschool lesson plan. My Kindergarten unit. I began my Kindergarten lesson plan because I was working in a class of 4-5-yr-olds. It was spring and the whole class of 20 couldn't talk about anything besides kindergarten. So, as I learned from my professor, I followed their interests. We did a whole month's lesson plans with Kindergarten as the theme.
We did things like a "Countdown to preschool Graduation" with a calendar and and graduation hat stickers, we did sorting activities with things we take to Kindergarten, and we went on a field trip to see a kindergarten class. Also, we charted how many kids were going to which schools.
I have looked back many times remembering how much fun that theme was for not only the kids, but for myself and my co-teacher, as well. I wondered why that was so much more successful than other preschool lesson plans. but I think it's simple. This was completely student directed curriculum. Because of that, they learned so much more than if we had done yet another unit about the zoo or ocean life.