This is more of an invitation to brainstorm with me, rather than a blog post:
Imagine you had the opportunity to team teach with a teacher from a different department. What course would you create?
…if you were teaching with a Humanities teacher?
…an art teacher?
…a science teacher?
…a language teacher (you choose the language)?
The Space Between the Numbers 
I’d like to do a course on argumentation, with a teacher of writing or language arts. It could include a historical element. We might draw on Anthony Weston’s “A Rulebook for Arguments”. If I found someone wonky enough perhaps we could bring out the differing standards for truth (epistemology?) across disciplines (which reminds me of http://xkcd.com/263/ — maybe another idea would be to have an interdisciplinary course on cartooning and math!)
I did have that opportunity! I did a 2 week (but 6 hours each day) course on historic experimentation. But another teacher did an amazing math-art seminar, and I loved what he did. I could easily see it transformed to a one semester course.
Would java or php qualify as “languages”? 😉
I work at an alternative high school program where last year we started with a interdisciplinary zombie unit. The social studies teacher used it for talking about geography and natural resources “If a zombie outbreak happened while you were vacationing in XXX, what resources would be abundant? What would be lacking?” (Another option would be to study WWII propaganda and create anti-zombie propaganda). The science teacher looked at how zombie-ism is transferred – would it make the most sense for it to be bacterial/viral/genetic/etc. ? As a math teacher I used it to look at exponential vs. logistic growth. The english teacher looked at undead lore from various societies (zombies / draugar / vampire / jiangshi / etc)
My home school is working on a video game creation course that will combine programming and digital art.