iPad recommendations

A great starting point for Objective-C and Cocoa in general:

Cocoa Programming for Mac OSX by Aaron Hillegaas
http://www.amazon.co.uk/Cocoa-Programming-Mac-OS-X/dp/0321503619/ref=sr_1_13?ie=UTF8&s=books&qid=1273592608&sr=8-13

Not read it, but considered *the* guide to Objective-C:

Programming in Objective-C by Stephen Kochan
http://www.amazon.co.uk/Programming-Objective-C-2-0-Developers-Library/dp/0321566157/ref=sr_1_1?ie=UTF8&s=books&qid=1273592595&sr=8-1

Good iPhone introductions:

Beginning iPhone 3 Development by Jeff LaMarche and Dave Mark
http://www.amazon.co.uk/Beginning-iPhone-Development-Exploring-SDK/dp/1430224592/ref=sr_1_11?ie=UTF8&s=books&qid=1273592608&sr=8-11

PragProg iPhone SDK Development
http://pragprog.com/titles/amiphd/iphone-sdk-development

More advanced:

More iPhone 3 Development by Jeff LaMarche
http://www.amazon.co.uk/More-iPhone-Development-Tackling-Professionals/dp/143022505X/ref=sr_1_1?ie=UTF8&s=books&qid=1273592763&sr=1-1

Topic-specific:

PragProg Core Animation by Bill Dudney
http://pragprog.com/titles/bdcora/core-animation-for-mac-os-x-and-the-iphone

PragProf Core Data by Marcus Zarra
http://pragprog.com/titles/mzcd/core-data

iPad-specific?
Just the PragProg beta book right now:
http://pragprog.com/titles/sfipad/ipad-programming

There's also Craig Hockenberry's new book but I've not purchased it yet:
http://appdevmanual.com/

He knows his stuff though.

If I was to just get two books, I'd get the Hillegaas book and Beginning iPhone 3 Development by Jeff LaMarche.