A collection of useful resources to help you master Common Lisp
There are many more excellent resources, most of them cross linked in one of the learning section.
There are many other great books you can find links to. These are the most popularly linked introductory works.
Following these are two more advanced books, but beginners shouldn't be afraid of them, they're quite accessible and "classics".
The last is actually on a related Lisp dialect, Scheme, but it's very helpful book, generally. If you find you prefer Scheme, it's an excellent start.
Quick-guides / cheat sheets for Common Lisp: