This is a basic tip, many gyms do this already, but we were hesitant to put a TV in front of a space where we normally like to focus. The key to the TV for us is content. You want to be able to maintain form, check yourself and run properly despite being on a treadmill and this can be hard to do if you're entirely engrossed in your soaps. That's why our next addition to the running room is...
Race Course DVDs
These videos from Outside Interactive are of famous runs like the Boston Marathon, famous locations like Central Park and the Charles River, and soon through parks. They include four different paces, mile markers that you can keep track of or start at, and directions for changing the incline on your treadmill to match the real world run. For us these make all the difference. Outside of the physical feeling of running on a treadmill, the most disheartening thing about being indoors is that you don't get anywhere (the gerbil wheel effect we call it). These solve that, and may even help you train for events you're running in.
We were using an old treadmill that had a belt that slowly was coming apart. Sure it had incline and a nice bounce not unlike a freshly mulched trail, but after trying a new model with better settings and way less noise we were hooked. The sound was key because we wanted to hear our TV/music. Tons of people are selling nice ones used, so check Craigslist for a good deal before you go to the store.
We used to use a little old boom box on full volume (see noisy treadmill we got rid of above) to jam out while running. We decided to get rid of it and put a cheap set of surround speakers around the room. In this way the treadmill might be, and it's odd to say this, better than running outdoors. You can put the music on without jamming something in your ear or worrying about your headphones coming out or getting snagged on something.
How do you make your treadmill experience better?