Esperanto, cutely referred to as Eo or Espo, is the most widely spoken constructed international auxiliary language on the globe.
If you would like to know more about Esperanto, please read its Wikipedia page (also in EO, Español, Italiano, and more.), which covers its history, current use, linguistic properties, and other very cool things.
To read blogs in Esperanto, check out the compiled blog list.
For other useful sites in Esperanto, check out the notable Esperanto list.
If you would like a site added to either list, please contact me.