HHmm not sure what technically constitutes a unit study but what I've done in the past is to find a few non-fiction resources (books, movies) and a few fiction sources (books). I then google the topic to find any cool craft, science experiments or look in my myriad of experiment books for something to go w/ it.

So for my DS5 who asked me about clouds today, I'll get the non-fiction Let's Read and find OUt science books about water cycle. I'll get a beautifully illustrated poem about the water cycle (beautiful words so tie in language arts, using descriptive words in painting a pic in the reader's mind, rythem of poetry). I will look for an easy reader for him to read to me about weather, clouds etc. I'll look for fiction picture books about a rainy day or some such thing. Additionally, we'll watch Magic School Bus episode on evaporation/water cycle. We'll then do an experiment to look at the water cycle. You put salt water in a bowl. In the center you put another bowl. You wrap tightly in saran wrap and put a rock in the center. This will guide the evaporating water to the center and it will drip into the inner bowl. When you have enough water condensed, you taste it to see that it's no longer salty and is drinkable. We might also discuss how Survivor Man used this method in the desert for survival and might google this method as a survival technique. WE'll put a glass of ice next to a boiling kettle and watch condensation form.

Well you get the picture.

I've done this with history as well...find a good historical fiction to go along w/ the history less, find pics to add to a timeline, read non-fiction sources, watch a movie etc.

Is that what you're referring to?
Dazey