Color Me Good

"Web-safe color, basically, is the set of colors that will render consistently in browsers on the two major computer operating systems (Windows and OS X). A true cross-platform Web-safe color palette is 216 colors." - Designing for the Web
The 216 Color Web Safe Pallete are the only colors that will render correctly on both PC and MAC
Visibone's Swatches

Be Accessible:
Use Contrast to make text readable. Do not use color to convey information. Example, Use an * to note a form field that is required not just changing the color to red.
You can check how you page will appear to different visual users at Vischeck.
You can also check a color before you use it on the Accessibility Color Wheel .

Tools:
Tons of Other Color Resources for Web Design
Genopal Online Tool
Geno Color gives a simple Color Lesson
HTML Color Names
Adobe Kuler
Color Lovers
http://wellstyled.com/tools/colorscheme2/index-en.html