Online Resources

On-line tutorials

Colin Allen & Maneesh Dhagat Lisp Primer
Online Tutorial to Common Lisp, Adaptive Remote Tutor.

References

Common Lisp, The Language, Second Edition. Guy L. Steele, Jr. Digital Press, ISBN: 1555580416
Usenet newsgroup: comp.lang.lisp
Contributed by Eric Moss (S02): Parenthetically Speaking (with Kent M. Pitman)
Free copy of ACL6.2.
Franz Inc. by David Cooper Jr.: Understanding Common Lisp (Basic Lisp techniques, pdf document).
Common Lisp, The Language, Second Edition. Guy L. Steele, Jr. Digital Press, ISBN: 1555580416, also on Reserve at the Math Library.
Allegro Common Lisp (ACL) online documentation. Slow (local on cse: Introduction, Contents, Index). Quicker (link to Franz's web page Introduction).
COMMON LISP: An Interactive Approach, by Stuart C. Shapiro
Common Lisp: A Gentle Introduction to Symbolic Computation, by David S. Touretzky
LISP FAQ by  Mark Kantrowitz.
... and much more from the Association of Lisp Users' page.