This site has multiple pages of documentation on the Arc language. The following is a table of contents. This is a work in progress, so I plan to add more as time permits.
Several interesting books are available free online: Paul Graham's On Lisp describes many of the concepts that ended up in Arc. Practical Common Lisp is a very interesting guide to Lisp, Common Lisp the Language is a good reference, and Structure and Interpretation of Computer Programs is perhaps the best way to learn Scheme.
Useful print books include
Paul Graham's ANSI Common Lisp,
the print editions of
Practical Common Lisp
and
Structure and Interpretation of Computer Programs
,
The Little Schemer
,
and Peter Norvig's
Paradigms of Artificial Intelligence Programming
.