I will keep updating this list as I find more tools

http://css3generator.com/

here you can generate css for  columns , transisitions etc

http://css-tricks.com/almanac/

great list of often forgotten css selectors and properties

http://blog.gfk.com/2014/05/2014-mobile-ux-design-trends-embracing-minimal/

This one isn’t a css tool but a worthwhile article on mobile design which css is a big part of