Below are some of links for further Adobe Photoshop CS4 materials:

Books -

Adobe Photoshop CS4 Classroom in a Book by the Adobe Creative Team		Photoshop CS4 Digital Classroom by Jennifer Smith and the Aquent Creative Team
Adobe Photoshop CS4 How-Tos: 100 Essential Techniques by Chris Orwig		Photoshop CS4 for Dummies by Peter Bauer
Real World Adobe Photoshop CS4 for Photographers by Conrad Chavez and David Blatner		Brilliant Photoshop CS4 by Steve Johnson
Photoshop CS4 Bible by Stacey Cates, Simon Abrams and Dan Moughamian		Adobe Photoshop CS4 on Demand by Steve Johnson and Perspection Inc.

Online training -

	Lynda.com tutorials for Photoshop CS4
		Length (hrs)
	Designing an Event Poster Hands-On Workshop	2.27
	Photoshop CS4 for Photographers: Desktop Printing Techniques	5.18
	Photoshop CS4 for the Web	6.77
	Photoshop CS4 Extended for 3D	4.58
	Photoshop CS4 Portrait Retouching Essential Training	12.38
	Photoshop CS4 for Photographers: Creative Color	4.5
	Photoshop CS4 for Photographers: Creative Effects	7.75
	Photoshop CS4 for Photographers: Camera Raw	7
	Photoshop CS4 One-on-One: Fundamentals	14.5
	Photoshop CS4 for Photographers	15
	Photoshop CS4 Essential Training	8.25
	Photoshop CS4 Getting Started	2
	Photoshop CS4 New Features	1.5