Hardware: What products are out there?
So, you're interested in Internet TV and are ready to take the plunge? The good news is this: you may not need to buy any new products. Many existing devices--most notably, the Xbox 360, PS3, and Wii--are already compatible with at least some Internet TV services.

Game consoles: Netflix is now available on all three current-generation home game consoles. The Wii and PS3 currently require a disc (available for free from Netflix) to stream content. The Xbox 360 requires no disc, but it does require an Xbox Live Gold membership (currently $60 per year). For pay-per-view movies and TV shows, the Xbox also supports Microsoft's Zune Marketplace, whereas the PS3 has its own PlayStation Store for buying and renting movies and TV shows. Xbox offers ESPN 3 (for users on supporting cable systems who already have ESPN), while the PS3 offers MLB TV.

Blu-ray players and home theater systems: In addition to playing DVDs and Blu-ray movies, most Blu-ray players also support several Internet TV options: Netflix, YouTube, Amazon or Vudu, and (coming soon on some models) Hulu Plus or Google TV. You'll want to seek out a player that offers built-in Wi-Fi, which makes connecting to these online services much more convenient.
See CNET's top-rated Internet-enabled Blu-ray players with Wi-Fi
DVRs: TiVo Series3 and Series4 DVRs offer built-in support for Netflix, Blockbuster, Amazon, and YouTube, with Hulu Plus support coming soon. Moxi DVRs support Netflix and Amazon via the PlayOn software (which runs on a networked PC elsewhere in your home).
Read the reviews of current TiVo DVRs
Read the reviews of current Moxi DVRs
TVs: Most major-brand TVs with online apps and widgets (sold in 2009 and 2010) usually offer an array of Internet TV services. Netflix is standard, along with Vudu or Amazon. Hulu Plus is coming to some TVs this fall, with more brands supported next year. Google TV will be built into a forthcoming Sony TV.
See CNET's top-rated Internet-connected TVs
PC to your TV: People have been enjoying Web-based video on their TVs for years thanks to an easy hack: simply connect the video output of a PC to your TV. The process is easier than ever in the age of HD, especially with most laptops and PCs now offering TV-friendly HDMI outputs. More-elegant (albeit more-expensive) solutions are also available: laptops equipped with Wireless Display let you "project" your PC desktop onto a TV via a $99 accessory. If you don't have a Wireless Display laptop, various "screen scraping" accessories accomplish the same thing.
Dedicated boxes
Dedicated hardware solutions for Internet TV are also available; these are the so-called "set-top boxes" that pioneered the Internet TV space. Many are $99 or less. Some of these models offer proprietary content or interfaces you can't get on the products mentioned above (iTunes content is only available on Apple TV, for instance). Others, such as Roku, offer mainstream streaming options (Netflix, Amazon, Hulu Plus), as well as more niche content that you won't find on mainstream boxes. Most of these boxes are also physically smaller than Blu-ray players and game consoles, so they'll fit in a TV cabinet that's already crowded with DVRs, game consoles, and disc players.

Apple TV ($99): The second-generation Apple TV is smaller and cheaper than its predecessor. Lacking the hard drive of the earlier model, the new Apple TV only supports video rentals (not purchases) from the iTunes Store. It also adds support for Netflix streaming.

Roku ($59-$99): Roku was the original "Netflix box" when it debuted in 2008. The company has since expanded the lineup, just refreshed for the fall of 2010. The latest Roku trio of models all support HD and--unlike Apple and Boxee--older standard-def TVs. The line-up starts at an ultra-affordable $59, too. More importantly, the capabilities of the Roku boxes have gone far beyond just Netflix. The boxes now offer dozens of video, photo, and music "channels," including Amazon, MLB TV, UFC, Vimeo, and Break.com, with Hulu Plus coming soon.
Boxee Box ($199, available November 2010): Boxee is already available as a free online media aggregator for Macs and Windows PCs (as well as hacked first-gen Apple TV units). The Boxee Box, manufactured by D-Link, aims to deliver that same experience to your TV screen. In addition to delivering a wide range of existing free online video and audio, the Boxee Box also aims to play nearly any digital media file via your home network or direct USB hookup. An included QWERTY remote control makes text searches and Web addresses easy to enter from the sofa.
Logitech Revue/Google TV (available fall 2010, price TBD): Details on this forthcoming Google TV box are still incomplete, but its aim is to deliver access to any Flash-based video on the Web, thanks to a fully integrated Chrome Web browser. Video-centric Google search will also be included, and Android-style apps will also be on board (by early 2011, anyway).
Other options
The WD TV Live Plus and Seagate FreeAgent GoFlex TV are so-called "USB media drives" that also offer support for Netflix (in addition to their primary mission of streaming video from attached hard drives). However, neither includes built-in Wi-Fi.