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A new Google Talk feature called Chatback lets you put up a widget on your website which lets visitors send messages directly to your Google Talk account. Your visitors, however, don't need a Google talk account; they can simply start writing messages directly into the widget. The chat opens up in a new window, so visitors can leave the actual site and keep chatting.
[img src="" caption="" credit="" alt=""]Chatback is based on an iframe, so it's not only for blogs; you can put it up pretty much on any website you want. Just go to the official Chatback page and grab the code.