Maybe "How To Design Programs"? (http://www.htdp.org/) I'm not sure if "Structure and Interpretation of Computer Programs" qualifies as a beginner's text, but that's also available online (http://mitpress.mit.edu/sicp/).
There's also "Scheme and the Art of Programming" and "The Little Schemer".
Does anyone here have good beginner books on Scheme? I'm thinking long-term; I don't expect functional mastery overnight.