Helper classes
Images
.img-responsive

Applies max-width: 100%; and height: auto; to the image so that it scales nicely to the parent element

.img-rounded

Adds rounded 3px border radius to the image

.img-circle

Makes image fully rounded

.img-thumbnail

Adds grey frame with white background color

.img-lg (*-sm, *-xs)

Optional custom sizing. Added specially for media lists

.img-* (*-10, *-15, *-20, *-30, *-40, *-50, *-60, *-70, *-80, *-90, *-100)

Optional image width

Styling
.border-*

Adds 1px border to the element, if it doesn't have it already. Available in 4 positions: top, bottom, left, right

.border-lg

Changes border width to 2px

.border-*-lg

You can specify border position: left, right, top and bottom

.border-xlg

Changes border width to 3px

.border-*-xlg

You can specify border position: left, right, top and bottom

.no-border-radius

Removes border radius from the element. To use add .*-top (bottom, left, right)

.cursor-move

Changes cursor style to move. Mostly used in sortable components

.cursor-pointer

Changes cursor style to pointer. Useful for user interaction feedback

.cursor-default

Changes cursor style to default

Positioning
.center-block

Set an element to display: block and center via margin

.position-relative

Changes element's positiion to relative

.position-static

Changes element's positiion to static

.pull-left

Float an element to the left with a class

.pull-right

Float an element to the right with a class

.clearfix

Easily clear floats by adding .clearfix to the parent element

.position-left

Add extra right margin to the element

.position-right

Add extra left margin to the element

Spacing
.m-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px margin to the element

.m-t-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px top margin to the element

.m-b-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px bottom margin to the element

.m-l-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px left margin to the element

.m-r-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px right margin to the element

.no-margin

Removes element's margin

.no-margin-top
(*-bottom, *-left, *-right)

Removes margin of the specified side

.p-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px padding to the element

.p-t-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px top padding to the element

.p-b-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px bottom padding to the element

.p-l-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px left padding to the element

.p-r-5
(*-10, *-15, *-20)

Add 5, 10, 15 and 20 px right padding to the element

.no-padding

Removes element's padding

.no-padding-top
(*-bottom, *-left, *-right)

Removes padding of the specified side