Another good option is to go to a particular channel's website to find episodes of your favorite shows. Often you'll be able to access recently aired episodes, and sometimes even complete seasons. For example, I'm usually busy on Sunday nights, but I've been able to catch Downton Abbey a day later on PBS.org for the past month. Although the stream's video quality is noticeably poorer than that of the TV broadcast, PBS gives me the option to buy and download each episode of its programming from iTunes in high definition. ABC and Fox offer similar options for many TV shows.
Still, finding what you're looking for among the mass of websites can be hard. That's where Clicker.com comes in: This website aggregates links to the legal video you want to see online, and then directs you to the provider's site, Hulu, Netflix, or iTunes. Not all of those options are free, but Clicker can save you time in trying to discover what shows are available. Even though going this route can sometimes leave you out of luck (no episodes of the first season of Modern Family are legally shown online, for example, so searching for those episodes returns nothing), you can use it to speed up your searches and rest assured that you're not violating any copyright law.
BBC iPlayer and iTV are two places to get British television online for free, but you have to be based in the United Kingdom to access them. One way to get around that requirement is to stream from a VPN using a server in the UK. (Several VPN providers can hook you up to a UK server; for general advice, check out our guide to using a VPN.)
Several sites promise to show you streams of live television or hard-to-find programming. Of course, they involve some caveats: Some of the content on these sites may not be legal, and watching or downloading the content could land you in trouble. Some of the sites also include lots of dead links, and you may end up paying for an experience that's not worth the price.
Tvduck.com finds all kinds of copies of specific shows online. Some of them are available for streaming only behind paywalls, some of them link to legal video on the producer's website, and some of them are illegally ripped copies of shows posted online.