Background classes:

#1abc9c
Turquoise
class="bg-turquoise"
#16a085
Green Sea
class="bg-green-sea"
#2ecc71
Emerland
class="bg-emerland"
#3498db
Peter River
class="bg-peter-river"
#16a085
Green Sea
class="bg-green-sea"
#2980b9
Belize Hole
class="bg-belize-hole"
#9b59b6
Amethyst
class="bg-amethyst"
#8e44ad
Wisteria
class="bg-wisteria"
#34495e
Wet Asphalte
class="bg-wet-asphalt"
#2c3e50
Midnight Blue
class="bg-midnight-blue"
#f1c40f
Sun Flower
class="bg-sun-flower"
#f39c12
Orange
class="bg-orange"
#e67e22
Carrot
class="bg-carrot"
#8e44ad
Pumpkin
class="#d35400"
#e74c3c
Alizarin
class="bg-alizarin"
#c0392b
Pomegranate
class="bg-pomegranate"
#ecf0f1
Clouds
class="bg-clouds"
#bdc3c7
Silver
class="bg-silver"
#95a5a6
Concrete
class="bg-concrete"
#7f8c8d
Asbestos
class="bg-asbestos"
#000000
Black
class="bg-black"
#ffffff
White
class="bg-white"

Special backgrounds:

#34495e
Base
class="bg-base"
#1abc9c
Firm
class="bg-firm"
#2ecc71
Success
class="bg-success"
#e74c3c
Danger
class="bg-danger"
#f1c40f
Warning
class="bg-warning"
#3498db
Info
class="bg-info"

Less mixins:

.clearfix()
When a floated element is within a container box, that element does not automatically force the container’s height to adjust to the floated element. When an element is floated, its parent no longer contains it because the float is removed from the flow. Use this mixin to fix this problem.
.center-block()
Center-align a block level element
.a-color(@color)
Link color
.a-color(@color; @color-active)
Link color for each of the two states (normal and hover)
.btn-background(@color)
Button background

CSS3 properties for crossbrowser compatibility

.border-radius(@radius)
Border Radius
.border-top-left-radius(@radius)
Border Radius for top left corner
.border-top-right-radius(@radius)
Border Radius for top right corner
.border-bottom-right-radius(@radius)
Border Radius for bottom right corner
.border-bottom-left-radius(@radius)
Border Radius for bottom left corner
.border-top-radius(@radius)
Border Radius for both top corners
.border-right-radius(@radius)
Border Radius for both right corners
.border-bottom-radius(@radius)
Border Radius for both bottom corners
.border-left-radius(@radius)
Border Radius for both left corners
.box-shadow(@shadow)
Box drop shadow
.transition(@transition)
Transition
.transition-delay(@transition-delay)
Transition Delay
.transition-duration(@transition-duration)
Transition Duration
.rotate(@degrees)
Transformation - Rotate
.scale(@ratio)
Transformation - Scale
.translate(@x, @y)
Transformation - Translate
.skew(@x, @y)
Transformation - Skew
.translate3d(@x, @y, @z)
Transformation - Translate in 3D
.transform-origin(@origin)
Transformation - Transform-origin
.backface-visibility(@visibility)
Backface visibility. Prevent browsers from flickering when using CSS 3D transforms. Default value is `visible`, but can be changed to `hidden`.
.background-clip(@clip)
Background clipping. Heads up: FF 3.6 and under need "padding" instead of "padding-box"
.background-size(@size)
Background sizing
.box-sizing(@boxmodel)
Box sizing
.content-columns(@columnCount, @columnGap)
CSS3 Content Columns
.hyphens(@mode: auto)
Optional hyphenation
.opacity(@opacity)
Opacity

Other mixins

.user-select(@select)
Select text on the page
.resizable(@direction)
Resize any element
.gradientBar( @primaryColor, @secondaryColor, @textColor, @textShadow )
Gradient Bar Colors for buttons and alerts
.reset-filter()
Reset filters for IE
.v-center()
Vertical centering

Base framework mixins

.font(@font-size,@color)
Change the font relative to the base font of the framework. (@font-size parameter in 'px')
.line-height(@line-height)
Change the line-height property relative to the base line-height property of the framework. (@line-height parameter in 'px')