The best books by far is http://pine.fm/LearnToProgram/

I also run a project named Hackety Hack: http://hackety-hack.com/ It
has a few lessons, but LtP is much more complete.

Next best is either
http://www.amazon.com/Ruby-Programming-Language-David-Flanagan/dp/0596516177/ref=sr_1_1?ie=UTF8&qid=1324400965&sr=8-1
or http://mislav.uniqpath.com/poignant-guide/

Some will recommend 'the pickaxe,' but I think it's pretty bad for beginners.