I watch TV through the clicker.com website, which is sort of a portal leading you to free and paid shows on network web sites and on the web sites of various cable channels. It makes it easy to find TV shows and web-only video. You can save a playlist of your favorite series and Clicker will email you when a new episode is added.
I'm running an Eris with stock Android 2.1, so I don't have full Flash video. Instead I load Clicker in the Skyfire browser. When Skyfire detects Flash video on a web page, it loads it onto the developers' servers, then pushes it back to you in a format that will play on your phone.
I watched last week's South Park this way on my bus ride to work this morning. Streamed smoothly the whole trip.