Navigation is an important part in a webpage. Done it right will help user to find what he needs in your pages. Some resources for navigation are below:

Webpages navigation

Sliding Doors of CSS - Sliding Doors of CSS, Part II

Vertical CSS menu with flyout submenu

Inverted Sliding Doors tabs

Bulletproof Slants

CSS Tabs 2.0

CSS Tabs with Submenus

Free Menu Designs

Mini-Tab Shapes

CSS navigation menu

Nifty Navigation Using CSS

List-O-Matic

CSS horizontal navigation list