Just search for a TV series like Mad Men or The Office, then click the "Show options..." button above the results. A panel appears on the left with several options; you can click "Videos" to narrow your search to videos, and after that the option to search for "Episodes" instead of "All videos."
Google knows how many seasons most shows have — it even listed two seasons for the Felicia Day web series The Guild — so you can pick the season you want to watch and see only those episodes. The search engine indexes numerous pay-based and advertising-supported video sites. It includes YouTube, Hulu, Vimeo, Amazon, Dailymotion, and network video sites like NBC.com, BBC.co.uk and AMCTV.com, among others.
This is just catch-up on Google's part, though. Television search engine startup Clicker has these features and more, but options are always welcome.
[via Search Engine Land]