This one is very detailed and can give a good start:

http://www.wpdesigner.com/2007/02/19/so-you-want-to-create-wordpress-themes-huh/

7 Useful PSD to WordPress Tutorials

PSD to CSS to WordPress

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PSD to WordPress Series

Free Bloopress WordPress Theme Design Tutorial with Source (PSD/xHTML/CSS/WordPress)

Creating a wordpress theme from a psd file

• Part 1 – Background / Introduction
• Part 2 – From .PSD to .HTML
• Part 3 – WordPress Structure
• Part 4 – The Header (header.php)
• Part 5 – The Footer (footer.php)

From PSD to HTML: Building a Set of Website Designs Step by Step

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