Formal transitions happen twice during a double-block period. My students have to move from one section of my extra-large classroom (3 classrooms merged into one) and move to another section for a new lesson with a new teacher. My students have two minutes to transition from session to session, and we play a variety of interesting music on the surround sound stereo system to keep it fun.
Communicating and collaborating with both colleagues and students' families is crucial in a blended environment. This is especially true if a teacher is doing something that looks very different from other teachers at his school. Check out how Aaron communicates and collaborates with both his colleagues at school and his students' families and how his methods of communication and collaboration have evolved over time.
During Live Investigation and Task sessions (both teacher-led), I often use a whole group discussion format just like a traditional classroom. Blended or not, there is no substitute for discussion.
The core ideas of my classroom are big ideas and themes that run through almost every lesson I teach. They are good math values, work values, life values. Whenever they come up during a lesson, I always explicitly make the connection. Next year, I plan on using a graphic for each value (some kind of eye graphic for core idea #1) to show, in my lessons, where the ideas come up.