Poll: How many development projects can you handle at once?

You may not want to turn down development work, but you also don't want to take on so many projects that things go off the rails. Developers, what's your project threshold?

I recently got myself into a bit of a bind. I had started a lot of projects, but then as soon as I got some traction on them, another project popped up and took priority. The next thing I knew, I had a stack of about seven major undertakings, as well as working with my day-to-day emergencies and queries. The upshot is that all of the "context switching" was killing me, and I had to refocus my energies on one project at a time to clear the backlog.

I think that three major projects is my threshold before things go off the rails. How deep can your development project pile get before it's too much for you to handle?