Auto compile LESS to CSS on write. Also will allow you to compile a parent script by putting /* lessc-parent: "main" */ on the top line

gistfile1.vim

function LessToCss()
  let match = matchstr(getline(1), '...lessc-parent: "\zs.\{-}\ze"')

  if strlen(match) > 0
    let current_file = match . ".less"
    let filename = match
  el
    let current_file = shellescape(expand('%:p'))
    let filename = shellescape(expand('%:r'))
  endif

  let command = "silent !lessc --line-numbers=mediaquery " . current_file . " " . filename . ".css"
  execute command
endfunction

autocmd BufWritePost,FileWritePost *.less call LessToCss()
autocmd BufReadPost,FileReadPost *.less set ft=css