For those who are new to blog carnivals (like myself!), Guillermo has put together a nice summary on his website that explains what is a blog carnival. Quite simply, it is just a collection of related blogs or websites that are submitted by readers and then have been summarized and listed into a single blog entry by the carnival host. A carnival may be compared to a magazine, in that various writers submit their articles to be published, and then the magazine editor reviews all the entries and puts them together into a final, polished magazine.
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With that, look for an official call for entries in the coming days. I will explain the submission process at that time. :)
In the meantime, I am happy to direct you to Guillermo's website GeoGebra Applet Central, where he is hosting the 20th edition of the Mathematics and Multimedia Carnival later in February.