A simple LESS style sheet that you can use in Bootstrap 3 to create columns of uniform height.

responsive-columns.less

// Courtesy of http://www.minimit.com/articles/solutions-tutorials/bootstrap-3-responsive-columns-of-same-height

.column-rules(@type) {
  .container-@{type}-height {
    display: table;
    padding-left: 0px;
    padding-right: 0px;
  }

  .row-@{type}-height {
    display: table-row;
  }

  .col-@{type}-height {
    display: table-cell;
    float: none;
  }
}

.column-rules(xs);
@media(min-width: @screen-sm-min) { .column-rules(sm); }
@media(min-width: @screen-md-min) { .column-rules(md); }
@media(min-width: @screen-lg-min) { .column-rules(lg); }

/* vertical alignment styles */
.col-top {
  vertical-align: top;
}

.col-middle {
  vertical-align: middle;
}

.col-bottom {
  vertical-align: bottom;
}