Let's start with a brief tour of streaming television online.
For quite a while, streaming television meant sitting and watching it on your computer. It wasn't ideal, for obvious reasons. Then, it got easier to sit and watch it on your phone. That wasn't ideal, either, if you liked the living-room experience. Tablets do a better job than phones of delivering a portable but less tiny experience.
But people who want TV to seem exactly like TV, the solution is either a smart TV, or some version of a set-top box. A set-top box might be your existing game console (like an Xbox or a PlayStation), your existing Blu-ray player, or a standalone device — most popularly (for the moment) an Apple TV if you're an Apple person or a Roku or Boxee device if you're not.
A set-top box uses your internet connection (some are wireless; some are wired) to stream content directly to your television, where it looks ... just like watching television. They can give you access to what you get from Hulu and Netflix, and they both have well-established purchase/rental outlets for things that don't stream free: on Apple TV you can use iTunes, and on the Roku, you can use Amazon Instant Video or Vudu, to name two.
Set-top boxes, depending on the one you pick, also have a bunch of other channels where you can get all kinds of other stuff, some of which is free, some of which requires a separate paid subscription (like MLB TV, which shows baseball), and some of which requires that you prove you have an existing subscription (like HBO GO, which will give you HBO content if you sign in as a cable subscriber who has HBO already). If you want to see how complicated this can get, look at this comparison chart, which is a year old but demonstrates the degree to which everybody's got a different collection of material.
As if this isn't all complicated enough, Apple will also let you get some content to your Apple TV by using apps on your iPhone or iPad and then beaming it from there to your television — that's how people with Apple TV get HBO GO, for instance. It's also how people with Apple TV have been able for a while to get the PBS programming that's available on the network's iPad app. PBS also streams lots of stuff on its regular site, but of course, that means sitting in front of your computer.
But this week, PBS unveiled a sprawling Roku channel that brings a massive haul of programs — science, drama, music, films, kids' stuff, and many of the other goodies public television has to offer — directly to the TVs of Roku users who have compatible boxes (apparently, not every Roku will work, but Engadget has a list of the ones that are compatible). There's a great deal of content here: a bunch of the documentaries I keep bothering you to watch (including the Wonder Woman one), some of Ken Burns' stuff, pieces from Great Performances, NOVA, Austin City Limits, and lots (and lots) more.
Cord-cutting (the industry term for getting rid of your cable subscription and getting everything through streaming) isn't yet a boom of any kind; it's happening steadily but is still a relatively unusual thing to do, as The New York Times reported recently. It's not clear, from the point of view of pure pragmatism, what the path is to breaking down the cable-bundle business model, given the intertwined content and cable universes (Comcast/NBC, most conspicuously). So far, you can't get HBO GO as a standalone, for instance, unless you subscribe the old-fashioned way — you theoretically can't, anyway.
But people are begging for it, and it's awfully hard not to notice as a consumer that if you have an average cable bill of $80 a month or so, you could at the moment subscribe to Netflix streaming and Hulu Plus and Amazon Prime, and you could purchase four other episodes of television a la carte per week in HD (that's on top of everything you can already stream on many broadcast and cable networks' sites) at three dollars a pop, and you'd still spend less than cable costs. And with Netflix making its own stuff now — including the upcoming new Arrested Development episodes — there are things you can't even get with your big cable bill.
And the easier it gets to pull great things from the internet to your television (not to mention the fact that a not-insignificant number of us can still simply pull broadcast channels in with an antenna), the more you can hear the tense creaking of these deeply bowed business models, which certainly feel like they've got to snap sometime.