A powerful Photoshop-like CSS gradient editor from ColorZilla. News: version 4 is here - radial and diagonal gradients, IE9 support, Sass support and more.
New in CS5, Adobe Kuler is present in Photoshop and Illustrator. It's a live palette item that features color palettes created by various designers from around the web (professional and non-professional).
You can save favorite palettes, browse the live palette library and submit your own palettes for consideration.
It's a great resource.