A large spectrum with most hex colors and a color picker to get the hex color code. Click Here

Responsive Mobile simulators:

Zemplate has some handy responsive simulators.  They don't replicate mobile devices perfectly, but they are a good start and allow you to troubleshoot the html using Firebug - which might be difficult using a phone or an iPad.  they have scrolling capabilities - without the scrollbar using up the space that other simulators have.  Click Here

Protostar Template for Joomla 3.0 with Bootstrap:

bj.zemplate.com: A web site focusing on the Protostar template for Joomla 3.0 with Bootstrap responsive styling

Twitter Cards

dev.twitter.com/docs/cards: Add meta tags for Twitter feeds to create Twitter Cards for links to your site