If you want to keep it legit(and I assume you do), really, your only options are services like Netflix and Hulu. You can *probably* do something like HBOGo. Pay for the subscription somewhere else(like your house!) and then let people using the TV at work sign on to that account. I'm guessing that most internet TVs won't have an HBOGo app, so you might have to buy a separate box like a Boxee Box or a Roku2.
You're most likely not going to find a live offering of tv channels that would simulate watching tv through the internet.