R.J.
Pirate-Free, or Legitimate-Free?
Legit Free
Hulu does the most recent 5 episodes for free. For the previous episodes (and previous seasons) Hulu+ is needed (know: there are still commercials, it's not like netflix streaming). Since they have a free trial period for Hulu+, you could do that and then either pay the $6 a month or cancel it and pay nada.
Station websites: Most only do the 3-5 most recent episodes, some have whole seasons. Really depends on the station.
Aside from those... it's pirating only for free shows as far as I know. Places like Vuze & Torrent sites