Clicker: (Another) One stop shop for web video
First off, in terms of content, it's hard to find a site with a better list of web video including network TV shows, webisodes, and high quality content from professional and amateur sources. The site is also extraordinarily easy to navigate. You can search for shows by title, genre, or media type (TV, movies, web shows, or music). Or you can just start typing in a search box to see what pops up. And results, with thumbnail images, will start to appear once you've entered a few letters.
One thing that's nice about Clicker is that right at the top of each show page is a link that tells you how many episodes are available online. Clicker doesn't host the videos, but rather scours the web for videos that are already online. If a video can be embedded in Clicker's site, it is, so you can watch without leaving the web page. If not, Clicker provides a link to the site where you can watch the video.
The site lets you subscribe to videos by creating playlists, and you have a nice array of options for each video. For instance, say you're watching one of the latest episodes of The Guild and decide you'd like to subscribe to the show. You can add all episodes to your playlist, just new episodes, or just the latest season. Then when you click your Playlist link, you can see a list of episodes you've watched or have yet to watch. There's also a "Season Pass" section that lets you see the shows you've subscribed to, although I'm guessing TiVo isn't going to be happy with Clicker co-opting its phrase for a series subscription.
You can request an invite for Clicker by visiting the service's homepage.