As you can see, Foundation has many ways to use and build your own mixins but there are a lot of mixins and mixin libraries out there that you might find useful for your projects. So, let's cover some of them:
Sass mixins available at http://sass-lang.com/documentation/file.SASS_REFERENCE.html#mixins
Bourbon is a Sass mixin library, available at http://bourbon.io/
Sassy buttons available at http://jaredhardy.com/sassy-buttons/
Sass CSS3 mixins available at http://mynameismatthieu.com/sass-css3-mixins/
8 Sass mixins you must have in your toolbox is available at http://zerosixthree.se/8-sass-mixins-you-must-have-in-your-toolbox/