Depend on which era you are looking for, I find mostly I have to create my own episode guides, as a lot of them are too unreliable and i prefer to go with continuity then by air date. tv.com is ok for it, but as its user edited its not a reliable source, the same is for wikipedia. epguides and pazaz.com is good sources for episode guides, searching the internet is another way of getting the info, fan sites I find can give reliable information.
Recently i downloaded an episode guide program application for the mac and its downloads the episode guides you need from
www.thetvdb.com. it's called tvseries and its very good info to have for any set creator.
i found this to be a very reliable source and it also has old tv series -
http://thetvdb.com/?tab=seasonall&id=71660&lid=7 - the living doll.