A set of useful LESS mixins. Based on: http://lesselements.com

elements.less

.gradient(@color: #F5F5F5, @start: #EEE, @stop: #FFF) {
  background: @color;
  background: -webkit-gradient(linear,
                               left bottom,
                               left top,
                               color-stop(0, @start),
                               color-stop(1, @stop));
  background: -ms-linear-gradient(bottom,
                                  @start,
                                  @stop);
  background: -moz-linear-gradient(center bottom,
                                   @start 0%,
                                   @stop 100%);
  background: -o-linear-gradient(@stop,
                                 @start);
  filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)",@stop,@start));
}
.bw-gradient(@color: #F5F5F5, @start: 0, @stop: 255) {
  background: @color;
  background: -webkit-gradient(linear,
                               left bottom,
                               left top,
                               color-stop(0, rgb(@start,@start,@start)),
                               color-stop(1, rgb(@stop,@stop,@stop)));
  background: -ms-linear-gradient(bottom,
                                  rgb(@start,@start,@start) 0%,
                                  rgb(@stop,@stop,@stop) 100%);
  background: -moz-linear-gradient(center bottom,
                                   rgb(@start,@start,@start) 0%,
                                   rgb(@stop,@stop,@stop) 100%);
  background: -o-linear-gradient(rgb(@stop,@stop,@stop),
                                 rgb(@start,@start,@start));
  filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)",rgb(@stop,@stop,@stop),rgb(@start,@start,@start)));
}
.bordered(@top-color: #EEE, @right-color: #EEE, @bottom-color: #EEE, @left-color: #EEE) {
  border-top: solid 1px @top-color;
  border-left: solid 1px @left-color;
  border-right: solid 1px @right-color;
  border-bottom: solid 1px @bottom-color;
}
.drop-shadow(@x-axis: 0, @y-axis: 1px, @blur: 2px, @alpha: 0.1) {
  -webkit-box-shadow: @x-axis @y-axis @blur rgba(0, 0, 0, @alpha);
  -moz-box-shadow: @x-axis @y-axis @blur rgba(0, 0, 0, @alpha);
  box-shadow: @x-axis @y-axis @blur rgba(0, 0, 0, @alpha);
}
.rounded(@radius: 2px) {
  -webkit-border-radius: @radius;
  -moz-border-radius: @radius;
  border-radius: @radius;
}
.border-radius(@topright: 0, @bottomright: 0, @bottomleft: 0, @topleft: 0) {
  -webkit-border-top-right-radius: @topright;
  -webkit-border-bottom-right-radius: @bottomright;
  -webkit-border-bottom-left-radius: @bottomleft;
  -webkit-border-top-left-radius: @topleft;
  -moz-border-radius-topright: @topright;
  -moz-border-radius-bottomright: @bottomright;
  -moz-border-radius-bottomleft: @bottomleft;
  -moz-border-radius-topleft: @topleft;
  border-top-right-radius: @topright;
  border-bottom-right-radius: @bottomright;
  border-bottom-left-radius: @bottomleft;
  border-top-left-radius: @topleft;
  .background-clip(padding-box);
}
.opacity(@opacity: 0.5) {
  -moz-opacity: @opacity;
  -khtml-opacity: @opacity;
  -webkit-opacity: @opacity;
  opacity: @opacity;
  @opperc: @opacity * 100;
  -ms-filter: ~"progid:DXImageTransform.Microsoft.Alpha(opacity=@{opperc})";
  filter: ~"alpha(opacity=@{opperc})";
}
.transition-duration(@duration: 0.2s) {
  -moz-transition-duration: @duration;
  -webkit-transition-duration: @duration;
  -o-transition-duration: @duration;
  transition-duration: @duration;
}
.transform(...) {
  -webkit-transform: @arguments;
  -moz-transform: @arguments;
  -o-transform: @arguments;
  -ms-transform: @arguments;
  transform: @arguments;
}
.rotation(@deg:5deg){
  .transform(rotate(@deg));
}
.scale(@ratio:1.5){
  .transform(scale(@ratio));
}
.transition(@duration:0.2s, @ease:ease-out) {
  -webkit-transition: all @duration @ease;
  -moz-transition: all @duration @ease;
  -o-transition: all @duration @ease;
  transition: all @duration @ease;
}
.inner-shadow(@horizontal:0, @vertical:1px, @blur:2px, @alpha: 0.4) {
  -webkit-box-shadow: inset @horizontal @vertical @blur rgba(0, 0, 0, @alpha);
  -moz-box-shadow: inset @horizontal @vertical @blur rgba(0, 0, 0, @alpha);
  box-shadow: inset @horizontal @vertical @blur rgba(0, 0, 0, @alpha);
}
.box-shadow(@arguments) {
  -webkit-box-shadow: @arguments;
  -moz-box-shadow: @arguments;
  box-shadow: @arguments;
}
.box-sizing(@sizing: border-box) {
  -ms-box-sizing: @sizing;
  -moz-box-sizing: @sizing;
  -webkit-box-sizing: @sizing;
  box-sizing: @sizing;
}
.user-select(@argument: none) {
  -webkit-user-select: @argument;
  -moz-user-select: @argument;
  -ms-user-select: @argument;
  user-select: @argument;
}
.columns(@colwidth: 250px, @colcount: 0, @colgap: 50px, @columnRuleColor: #EEE, @columnRuleStyle: solid, @columnRuleWidth: 1px) {
  -moz-column-width: @colwidth;
  -moz-column-count: @colcount;
  -moz-column-gap: @colgap;
  -moz-column-rule-color: @columnRuleColor;
  -moz-column-rule-style: @columnRuleStyle;
  -moz-column-rule-width: @columnRuleWidth;
  -webkit-column-width: @colwidth;
  -webkit-column-count: @colcount;
  -webkit-column-gap: @colgap;
  -webkit-column-rule-color: @columnRuleColor;
  -webkit-column-rule-style: @columnRuleStyle;
  -webkit-column-rule-width: @columnRuleWidth;
  column-width: @colwidth;
  column-count: @colcount;
  column-gap: @colgap;
  column-rule-color: @columnRuleColor;
  column-rule-style: @columnRuleStyle;
  column-rule-width: @columnRuleWidth;
}
.translate(@x:0, @y:0) {
  .transform(translate(@x, @y));
}
.background-clip(@argument: padding-box) {
  -moz-background-clip: @argument;
  -webkit-background-clip: @argument;
  background-clip: @argument;
}

//Centered object
.centered(@width, @height, @padding) {
position: fixed;
top: 50%;
left: 50%;
width: @width;
height: @height;
margin-top: -@height / 2 - @padding;
margin-left: -@width / 2 - @padding;
padding: @padding;
}

//3D TEXT MIXIN 
.3D-Text(@color,@depth) {
/* @color - The base color for the text. (Ideal range: 15% - 95% Brightness)
@depth - Height of the letters, (Ideal Range: 0.4x - 2.5x) */
font-weight:bold;
/* 3D Effect works best on fat text. Take this out and make it lean if you want. */
color:@color;
/* Sets the font color to the base value. */
text-shadow:
/* This is where the vertical stack and shadows get built, in a process described by top scientists as "magic" */
/* Hightlight 100% */
0 (@depth*0.01em) 0 lighten(@color,3.3%),
/* Vertical Stack: 40% Shadow */
0 (@depth*0.02em) (@depth*0.01em) darken(@color,10%),
/* Vertical Stack: 36% Shadow */
0 (@depth*0.03em) (@depth*0.02em) darken(@color,11%),
/* Vertical Stack: 34% Shadow */
0 (@depth*0.04em) (@depth*0.02em) darken(@color,13%),
/* Vertical Stack: 31% Shadow */
0 (@depth*0.06em) (@depth*0.01em) darken(@color,16%),
/* Immediate Sharp Shadow */
0 (@depth*0.06em) (@depth*0.03em) rgba(0,0,0,.5),
/* Sharp Top Shadow */
0 0 (@depth*0.05em) rgba(0,0,0,.2),
/* Small Side Shadows */
0 (@depth*0.02em) (@depth*0.08em) rgba(0,0,0,.3),
/* Main Bottom Shadow, Blurred */
0 (@depth*0.1em) (@depth*0.12em) rgba(0,0,0,.25),
/* Large Diffused Bottom Shadow */
0 (@depth*0.2em) (@depth*0.20em) rgba(0,0,0,.15); }