My base mixins

_mixins.scss

// Mixins

@mixin clearfix-overflow{
  overflow: hidden;
  _overflow: visible;
	zoom: 1;
}
	
@mixin boxEmboss($opacity, $opacity2){
    box-shadow:white($opacity) 0 1px 0, inset black($opacity2) 0 1px 0;
}
// USAGE: .box{ @include boxEmboss(0.8, 0.05); }

@mixin letterpress($opacity){
    text-shadow:white($opacity) 0 1px 0;
}

// http://nicolasgallagher.com/another-css-image-replacement-technique/
@mixin hideText{
	font: 0/0 a;
	text-shadow: none;
	color: transparent;
}

@mixin navigation-list {
	list-style-type: none;
	padding: 0;
	margin: 0;
	overflow: hidden;
	> li{
		display: block;
		float: left;
		&:last-child{
			margin-right: 0;
		}
	}
}
	
@mixin border-radius($topleft:5px,$topright:null,$bottomright:null,$bottomleft:null) {
  @if $topright != null and $bottomright != null and $bottomleft != null {
    border-top-left-radius: $topleft;
    border-top-right-radius: $topright;
    border-bottom-right-radius: $bottomright;
    border-bottom-left-radius: $bottomleft;
    -moz-border-radius-topleft: $topleft;
    -moz-border-radius-topright: $topright;
    -moz-border-radius-bottomright: $bottomright;
    -moz-border-radius-bottomleft: $bottomleft;
    -webkit-border-top-left-radius: $topleft;
    -webkit-border-top-right-radius: $topright;
    -webkit-border-bottom-right-radius: $bottomright;
    -webkit-border-bottom-left-radius: $bottomleft;
  } @else {
    -webkit-border-radius:$topleft;
    -moz-border-radius:$topleft;
    border-radius:$topleft;
  }
}

@mixin box-shadow($first, $second:null) {
   @if $second != null {
      -webkit-box-shadow:$first,$second;
      -moz-box-shadow:$first,$second;
      box-shadow:$first,$second;
   } @else {
      -webkit-box-shadow:$first;
      -moz-box-shadow:$first;
      box-shadow:$first;
   }
}

@mixin transition($property,$delay:.2s,$easing:linear) {
  -webkit-transition:$property $delay $easing;
  -moz-transition:$property $delay $easing;
  -o-transition:$property $delay $easing;
  -ms-transition:$property $delay $easing;
  transition:$property $delay $easing;
}

@mixin background-gradient($top_color:#fff,$bottom_color:#e6e6e6) {
   background-image: -webkit-gradient(linear, 0 0, 0 100%, from($top_color), color-stop(25%, $top_color), to($bottom_color));
   background-image: -webkit-linear-gradient($top_color, $top_color 25%, $bottom_color);
   background-image: -moz-linear-gradient(top, $top_color, $top_color 25%, $bottom_color);
   background-image: -ms-linear-gradient($top_color, $top_color 25%, $bottom_color);
   background-image: -o-linear-gradient($top_color, $top_color 25%, $bottom_color);
   background-image: linear-gradient($top_color, $top_color 25%, $bottom_color);
   filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#{$top_color}', endColorstr='#{$bottom_color}', GradientType=0);
}

@mixin vendor-prefix($name, $argument) {
  -webkit-#{$name}: $argument;
  -ms-#{$name}: $argument;
  -moz-#{$name}: $argument;
  -o-#{$name}: $argument;
  #{$name}: $argument;
}
  	
@mixin border-radius($argument) {
  @include vendor-prefix(border-radius, $argument);
}	
 
@mixin box-shadow($argument) {
  @include vendor-prefix(box-shadow, $argument);
}

@mixin opacity($int) {
  filter: alpha(opacity=$int);
	-moz-opacity:$int/100;
	opacity:$int/100;
}

@mixin input-placeholder-color($color) {
  &::-webkit-input-placeholder { color: $color; }
  &:-moz-placeholder { color: $color; }
  &:-ms-input-placeholder { color: $color; }
}