I like to listen to music while I run. I love to get lost in the songs and sometimes find myself air-drumming while I run. I've gotten some strange looks along the way but when you are running barefoot or in funky minimalist shoes, you get strange looks anyway, right? Other than that, I usually try to think of anything but work. For me, the music helps with the zoning-out (like meditation).
On a side note, for the math folks above... A friend of mine told me he would try to come up with the numerical value of different words where A=1 and Z=26. Each letter gets a numerical value, then add it up. He said he would do that while playing soccer and would calculate the names of the other players for fun. I'm no math wiz (actually a lawyer and we all know us lawyers dont do numbers) but thought you might find that entertaining for your long runs.
On a side note, for the math folks above... A friend of mine told me he would try to come up with the numerical value of different words where A=1 and Z=26. Each letter gets a numerical value, then add it up. He said he would do that while playing soccer and would calculate the names of the other players for fun. I'm no math wiz (actually a lawyer and we all know us lawyers dont do numbers) but thought you might find that entertaining for your long runs.