I've come to accept these interruptions as a fact of life that I have only modest control over. My wife and I have worked out a system of "don't interrupt me, I need to focus" indicators, but my work environment (aka. cube farm) doesn't help.

In my circumstance, the problem stems from coworkers with some form of ADD, either learned or biological. This becomes obvious in meetings as they interrupt me (and each other), fail to stick to meeting agendas, fail to address pressing issues, etc. I used to find it irritating until I realized that it yields certain benefits for me.

The way I deal with it is exercise: tai chi, running, and bicycling.