Here are a pair of handy tools for checking accessibility and effectiveness of your website designs:

Spur – This tool analyzes your page and allows you to put yourself in the position of a user with visual impairments through desaturating your page (color blindness), blurring the content or increasing contrast.  These lenses also help you see what content stands out on your page at a glance.

Snook – This basic color contrast checker is very handy and easy to use.  You can quickly check your fonts vs. your background colors to see if you’re hitting the accessibility mark at different sizes.