And other options - as an example, I have the Netflix app on my iPad (and an account w/ them) and via my home Wi-Fi network can watch their offerings - viewed an episode of Bones recently. I'm sure others will 'chime in' w/ their favs!
If you are in the USA, you can acquire network broadcast apps like ABC, NBC, USA. CBS does not have an app but you can get Netflix and see CBS shows. Hulu+ is also available.
In Britain, Canada, Australia and several other countries, there's BBC iPlayer, which allows you to watch some really good TV shows. It's a subscription service outside the UK.