A sample of using fontello in a .LESS project

Font.less

@charset "UTF-8";

@font-face {
  font-family: 'groovy';
  src: url('/ext/font/groovy.eot');
  src: url('/ext/font/groovy.eot?#iefix') format('embedded-opentype'),
       url('/ext/font/groovy.woff') format('woff'),
       url('/ext/font/groovy.ttf') format('truetype'),
       url('/ext/font/groovy.svg#groovy') format('svg');
  font-weight: normal; font-style: normal; 
}

.groovy() {
  font-family: groovy; 
  font-style: normal;
  speak: none;

  display: inline-block;
  width: 1.1em;
  margin-right: .1em;
  text-align: center;
}

.begroovy(@content, @size) {
  .groovy(); 
  font-size: @size; 
  content: @content;
}

.begroovy(@content) {
  .groovy();  
  content: @content;
}

[class^="icon-"], [class*=" icon-"] {
  .groovy();
}

// RSS
.icon-rss:before { content: '\e73a'; } /* '' */
.icon-rss-alt:before { content: '\e73b'; } /* '' */

// Admin
.icon-doc:before { content: '\1f4c4'; } /* '\1f4c4' */
.icon-pencil:before { content: '\270e'; } /* '✎' */
.icon-trash:before { content: '\e729'; } /* '' */
.icon-cog:before { content: '\2699'; } /* '⚙' */
.icon-thumbs-up:before { content: '\1f44d'; } /* '\1f44d' */

// Admin Post Buttons
.icon-comment:before { content: '\e718'; } /* '' */
.icon-font:before { content: '\e779'; } /* '' */
.icon-bold:before { content: '\e77a'; } /* '' */
.icon-italic:before { content: '\e77b'; } /* '' */
.icon-indent-left:before { content: '\e783'; } /* '' */
.icon-github:before { content: '\f308'; } /* '' */
.icon-video:before { content: '\1f3ac'; } /* '\1f3ac' */
.icon-camera:before { content: '\1f4f7'; } /* '\1f4f7' */
.icon-attach:before { content: '\1f4ce'; } /* '\1f4ce' */
.icon-link:before { content: '\1f517'; } /* '\1f517' */

// Conformation
.icon-ok:before { content: '\2713'; } /* '✓' */
.icon-cancel:before { content: '\2715'; } /* '✕' */

// Contact
.icon-facebook-rect:before { content: '\f301'; } /* '' */
.icon-twitter-bird:before { content: '\f303'; } /* '' */
.icon-mail:before { content: '\2709'; } /* '✉' */

// Menu
.icon-left-open:before { content: '\e75d'; } /* '' */
.icon-right-open:before { content: '\e75e'; } /* '' */

// Misc
.icon-tags:before { content: '\e70d'; } /* '' */
.icon-calendar:before { content: '\1f4c5'; } /* '\1f4c5' */
.icon-globe:before { content: '\1d30d'; } /* '\1d30d' */
.icon-pin:before { content: '\1f4cc'; } /* '\1f4cc' */
.icon-search:before { content: '\1f50d'; } /* '\1f50d' */

Usage.less

h1 {
  font-size: 24px;
}

h1:before {
  .begroovy('\2699', 20px);
}