|AppleScript: The Definitive Guide, 2nd Edition||
On the tech support bookshelf. More reference than tutorial, covers everything.
|Apple Training Series: AppleScript 1-2-3||
On the tech support bookshelf. Teaches AppleScript in detail.
|Learn AppleScript: The Comprehensive Guide to Scripting and Automation on Mac OS X (Learn (Apress))||
Not on my bookshelf, but the authors are highly respected in the AppleScript community.
|AppleScript: A Beginner's Guide||
This is new, so it should be up to date. So far, the one review says it isn't so good. Buyer beware.
|AppleScript: The Missing Manual||
Old (maybe out of date in places) but highly recommended by others.
|AppleScript in a Nutshell: A Desktop Quick Reference (In a Nutshell (O'Reilly))||
Older title, on the tech support bookshelf.
|Riding the Helix Express||
No scripting, but it's the Classic Helix resource, so I had to link to it.