Featured means that they have been seen or listed or written on these websites.
For example, Suppose, Forbes writes an article about "Shout me loud is the biggest blogging community".
Now, apparently, this means, Shout me loud has been featured on Forbes and once the article is published, ShoutmeLoud can proudly say that they have been featured in such websites. Got it?
And on Internet, one might definitely know one of these online brands, so it adds a trust factor to the website.