The page https://electricimp.com/docs/resources/learningsquirrel/
has the following link to a Squirrel tutorial:
http://forum.iv-multiplayer.com/index.php?topic=5267.0
The domain seems to be still active, but the forum is not reachable.
Some member found an archive:
https://web.archive.org/web/20130719134536/http://forum.iv-multiplayer.com/index.php/topic,5267.0.html
@beardedinventor: Maybe this link could be updated in the learning Squirrel page…