Smashing Magazine have 53 CSS-Techniques You Couldn’t Live Without and also a new list of 50 CSS-techniques, ideas and ready-to-use solutions for effective coding.

This is the famous "20 CSS Tips and Tricks" listed by Pete Freitag.

1. Rounded Corners
2. Rounded Corners without images
3. Creating a Netflix style star ratings
4. Tableless forms
5. Styling Lists with CSS
6. 2 Column Layout Technique
7. 3 Column Layout with CSS
8. 3 Column Fixed width centered layout
9. Printing with CSS
10. Adding a CSS stylesheet to an RSS feed
11. Footer Stick
12. CSS Element Hover Effect
13. Styling Horizontal Rules
14. Clearing Floats
15. CSS Popups
16. Box Punch
17. CSS Badge
18. Orange RSS Buttons with pure CSS
19. 10 CSS Tricks you may not know
20. 10 More CSS Tricks you may not know
21. Spiffy Corners - Rounded corners without images or script
22. More rounded corners with CSS

Other tips and tutorials

1. Complete layout techniques and tutorials - from MaxDesign
2. 12 useful CSS templates - easy to understand
3. CSS template gallery - Awesome collection of CSS template
4. Advanced CSS layout - Step by step guide
5. Businesslogs' 5 CSS Tips
6. Creating a Style-Guide for your site

Droppyale's list of CSS tips

1. Turning a list into a navigation bar
2. How To Clear Floats Without Structural Markup
3. A CSS styled table
4. Generating Dynamic CSS with PHP
5. A CSS Framework
6. Avoiding classitis
7. Architecting CSS
8. Creating a Star Rater using CSS
9. Introducing the CSS3 Multi-Column Module
10. In search of the One True Layout
11. One clean HTML markup, many layouts
12. PHP + CSS Dynamic Text Replacement (P+C DTR)