We gave up on the whole letter a week theme school idea. It was cute but required too much preparation time that I don't have with a new infant in the home. I decided, after our field trip to the Northeast, to set up a Time Machine and we would go back in time to different time periods instead. This has worked amazingly well because we are able to study any aspect of life that occured in whatever particular span of time. For example, we can study art, math, language, literature, poetry, science, astronomy, philosophy, history of course, and any other specific subject because it all happened in history. I have liked studying things in a historically chronological order. It makes any new information I get fit better in my mind:)
There was one last themed week before our trip...C is for Camera. We studied light and made a pinhole camera. It took us the whole week, but it is a very fun project to do with your kids. You can actually take a real picture with it and get it developed. Very fun! The kids will always remember this one:) More posts on the trip in the next couple days! (I'm probably lying).