Shout Box

Like a simple chat room, or a forum reduced to a single thread. Commonly placed on the main page of a website.

Many Web Comics don't have a large enough community to support a full-size, separate message board. A Shout Box is one way to provide easy, highly-visible interactivity.

See also The Rant.

Examples of Shout Box include:

Alien Dice' uses one for comics and newsposts, even though it does have a forum.
Beyond Reality has bot one of these and a forum.
Dream Catcher uses one.
Users of Deviant ART who subscribe have the option to put a shoutbox with any journal they post.
Brat-halla has embedded a single, blog-powered comment thread for a similar effect.
MYSHOUTBOX (seriously, they put it in all caps like that) is used by Juathuur.
Tom Siddell of Gunnerkrigg Court used the home-encoded comment thread for Painting the Fourth Wall during the interim comic City Face: instead of displaying Real Life reader comments, it displayed comments from the Animated Actors and other in-universe characters reading the comic within the comic. They're archived here.
Bear And Kitten had a very avid fanbase that actively posted in their shoutbox. Oddly enough, even though the webcomic hasn't update in almost a year now, the fans still post in the shoutbox because they actually became a close knit group of friends. Seemingly forgetting that they even came to the website for the comic.
- Currently the site is down, but the shoutbox is still accessible via internet archive.
Conversely, Bizarre Uprising's shoutbox has consisted primarily of complaints of They Changed It, Now It Sucks vis-a-vis the Time Skip.
Planet Zebeth uses one as well.