We have a our treadmill in the basement, mostly because we have space and it doesn't disturb anyone else when it's down there. We have a TV built into the Reebok model we got (I don't recommend that), but you have to look down to watch it. I didn't mind, but my wife hated it.
So I knocked together a shelf unit to hold our old TV. We put our 31" tube model down there, so I went for sturdy rather than aesthetic.
In any case, it's nice to watch TV down there while running and it helps to pass the time a bit rather than staring out the wall or out the window. I run with music at times, but it's more motivating and distracting if I know I can see something in front of me.
My wife watches her horse training tapes, trying to be more efficient with her time and learn a few things. That works out well for her, but I'm not that interested in those. I tried watching some sitcoms we have on DVD (Heros, Northern Exposure), but 15-20 minutes of those leaves you hanging more often than not.
So I moved on to watching movies. I tried "The Matrix" first, one of my favorites, and since then I've gone through "The Fantastic Four", "Goldfinger", "Hoosiers" and now "Iron Man", each of them 15-20 minutes at a time as I run. It seems that matches up well with the chapters and I haven't had much issue re-watching some parts. I tend to pick action movies since dialog is hard to hear and you want something light, but I might try some comedies as I run out of things to watch.
I recommend trying a TV near the treadmill, even if you like music. You can always have an iPod or something playing in there, but being able to pop on a movie is great.