Design

Interaction Design Pattern library

Describes common patterns of navigation, searching, shopping and more. Gives examples, pros, cons and use cases. Good for showing clients examples of what we mean when we say, for example, "accordian nav".

http://www.welie.com/patterns/index.php

10 Useful Usability Findings and Guidelines

http://www.smashingmagazine.com/2009/09/24/10-useful-usability-findings-and-guidelines/

What to put in website footers 

http://www.smashingmagazine.com/2009/06/17/informative-and-usable-footers-in-web-design/

Call to Action Buttons: Examples and Best Practices

http://www.smashingmagazine.com/2009/10/13/call-to-action-buttons-examples-and-best-practices/

Minimising Complexity in User Interfaces

http://www.smashingmagazine.com/2009/10/07/minimizing-complexity-in-user-interfaces/

The Four Key Components of a Great Web Design

http://webdesignledger.com/tips/the-four-key-components-of-a-great-web-design

Generate colour schemes with Adobe Kuler

http://kuler.adobe.com

Colour charts sorted by HSB

For picking lighter shades of a given colour, it is best to keep the same "hue" and "saturation" and just vary the "brightness". These colour charts show each hue and gives you hex colours for their different saturations or brightness.

http://www.december.com/html/spec/colorhues.html

Background Patterns

http://subtlepatterns.com/

CSS Background Gradients

http://www.colorzilla.com/gradient-editor/