Web instant-messaging startup Meebo has told us it will launch chat rooms for its users tonight, including a pretty neat feature that embeds video and other media into the discussion (see below). Update: Sorry! Widget removed; moderation was too intensive. Screenshot below.

Some nice aspects: you don’t need a login to use Meebo Rooms, you can embed the same room just about anywhere, and you can make private rooms or also try get your room featured on Meebo.com. To include a piece of video, picture, or music you simply type its URL into the chat form — initially YouTube, Flickr, deviantART, Google Video, and any MP3 are supported.

This is an obvious branding opportunity, and sites like CNET, Flixster, Sony Jive, and PopSugar have signed on to have their own sponsored rooms, which fans can embed on their own pages and blogs. The very same real-time chat is displayed anywhere the widget is located. On regular players, Meebo shows ads during lulls in viewing.

The big feature I’d like to see added is the option to make video viewing simultaneous, where one participant determines what everybody else watches at the same time. At this point I don’t see any way to do that.

Meebo Rooms is an extension of the company’s MeeboMe widget, which allowed site owners to have one-on-one chats with visitors to their sites right on the page.

Other companies we’ve written doing group video viewing are SideKlick (which requires a download), ClipSync (which is simultaneous), and YouTube. But the easily spreadable Meebo widget is a step up.

Update: If you are reading Monday night, come visit the site! We are chatting live with Meebo CEO Seth Sternberg at the moment.

Disclosure: Meebo is funded by True Ventures, as is GigaOM.