Ido was created in 1907 as a set of proposed reforms for the international auxiliary language Esperanto. The reform proposals were not universally accepted, but enough people liked Ido that there continue to be Ido speakers to this day.
An advantage of Ido is that it is close enough to Esperanto that Esperanto-speakers and Ido-speakers can understand each other. Also, Ido, unlike Esperanto, doesn't use any special letters so is more adapted for Internet use.
Sadly, there are often bad feelings between Esperantists and Idoists based on the events of 1907. In the opinion of this writer, fighting over which international auxiliary language is better just makes all of us look bad. It's better to try to get along! After all, we speak pretty much the same language.
The Our Father in Ido
Patro nia, qua esas en la cielo,
tua nomo santigesez;
tua regno advenez;
tua volo facesez quale en la cielo
tale anke sur la tero.
Donez a ni cadie l'omnidiala pano,
e pardonez a ni nia ofensi,
quale anke ni pardonas a nia ofensanti,
e ne duktez ni aden la tento,
ma liberigez ni del malajo.
Uniono por la Linguo Internaciona Ido (ULI)
Wikipedio - Wikipedia in Ido
Ido in English Wikipedia
The International Language Ido (UK)
Parolez Ido - social network in Ido
Ido-librerio - PDF books in Ido including the Gospel of Luke
The Lord's Prayer in Ido at Christus Rex
Ido-English Dictionary - can be downloaded
Ido at Kafejo.com - page in English, many links
Ido - la linguo maxim facila (in Italian, English and Ido)
Bible: Ecclesiates, Chapter 1 in Ido (with audio)
Bible: Ecclesiates 1:1-6 (different translation)
Polona Ido-Lernolibro: PDF
If you know of other good Ido links, please add them in a comment