The following communication analyses the weblogs, though they emerge in the beginning of internet only in the last years they have became popular. Nowadays they are real alternative means of communication, the weblogs are high value informative resources. This phenomenon, the typologies than can be found, their features, origins and evolution will be analysed. Finally, a brief comment on the more relevant blog searchers the and directories, together with the most important Spanish weblogs on librarian science and documentation.