mice.css

.mouse, #preview{
  position: absolute;
  background-repeat: no-repeat;
  height: 22px;
  min-width: 15px;
  z-index: 100;
}

.mouse{
  background-image: url('../images/cursor.png');
}

span.chat{
  -moz-border-radius:5px;
  -webkit-border-radius:5px;
  border-radius:5px;
  background-color:#222;
  box-shadow:0 1px 0 #fff;
  color:#fff;
  font-size: 12px;
  margin: 0 0 0 15px;
  display: block;
  opacity: 0.75;
  font-size: 12px;
  line-height: 16px;
  padding: 2px 5px;
  float:right;
}

span.mouse img, span#preview img{
  padding: 0 5px;
  float:left;
  margin: 0 -15px 0 15px;
  width: 20px;
  height: 20px;
}


form
{  
  margin: 0px 0px 0px -10px;
  width:470px;
}

form#chat input{
  width: 185px;
  border:0;
  padding:10px;
  margin:10px;
  -moz-border-radius:5px;
  -moz-box-shadow:0 1px 0 #fff;
  -webkit-border-radius:5px;
  -webkit-box-shadow:0 1px 0 #fff;
  border: 5px #bbb solid;
  
}

mice.js

io.setPath('/js/socket/');

function ratelimit(fn, ms) {
  var last = (new Date()).getTime();
  return (function() {
    var now = (new Date()).getTime();
    if (now - last > ms) {
      last = now;
      fn.apply(null, arguments);
    }
  });
}

function move(mouse){
  if(disabled == false){                               
    if($('#mouse_'+mouse['id']).length == 0) {
      $('body').append('<span class="mouse" id="mouse_'+mouse['id']+'"><span style="display:none;" class="chat"/></span>');
    }
    $('#mouse_'+mouse['id']).css({
      'left' : (($(window).width() - mouse['w']) / 2 + mouse['x']) + 'px',
      'top' : mouse['y'] + 'px'
    })
  }
};

function speak(data){
  clearTimeout(timeouts[data['id']]);
  $('#mouse_'+data['id']+' img').remove();
  $('#mouse_'+data['id']).append('<img src="http://www.gravatar.com/avatar/' + data['email'] + '?s=20" />');

  if(data['text'] == '') {
    return $('#mouse_'+data['id']+' .chat').hide();
  }

  $('#mouse_'+data['id']+' .chat').show().html(data['text']);
  timeouts[data['id']] = setTimeout("$('#mouse_"+data['id']+" .chat').hide()", 5000)
};

function preview(data){
  clearTimeout(timeouts[data['preview']]);
  $('#preview img').remove();
  $('#preview').append('<img src="http://www.gravatar.com/avatar/' + data['email'] + '?s=20" />');

  if(data['text'] == '') {
    return $('#preview .chat').hide();
  }

  $('#preview').show();
  $('#preview .chat').show().html(data['text']);
  timeouts['preview'] = setTimeout("$('#preview').hide()", 5000)
};

$(document).ready(function(){
  $('#mouse_toggle a').toggle(function(){
    $('.mouse').hide();
    disabled = true;
    $(this).html('enable');
  }, function(){
    $('.mouse').show();
    disabled = false;
    $(this).html('disable');
  });

  $('form#chat input#email').focus();
  $('form#chat').submit(function(){
    if($('form#chat input#email').val() == '') {
      return alert('You forgot to fill in your e-mail address.');
    }

    socket.send(JSON.stringify({
      action: 'speak',
      email: $('form#chat input#email').val(),
      text: $('form#chat input#text').val().substring(0, 140)
    }));

    email: $('form#chat input#text').val('')
    return false;
  })

  $('body').append('<span id="preview"><span style="display:none;" class="chat"/></span>');
});

$(document).mousemove(
  ratelimit(function(e){
    socket.send(JSON.stringify({
      action: 'move',
      x: e.pageX,
      y: e.pageY,
      w: $(window).width(),
      h: $(window).height()
    }))

    $('#preview').css({
      'left' : e.pageX + 'px',
      'top' : e.pageY + 'px'
    })
  }, 40)
);

var disabled = false,
    socket = new io.Socket('jeffkreeftmeijer.com', {port: 8000}),
    timeouts = {};

if(socket.connect()){
  socket.on('message', function(data){
    data = JSON.parse(data);
    if(data['action'] == 'close'){
      $('#mouse_'+data['id']).remove();
    } else if(data['action'] == 'speak') {
      if(data['id']) {
        speak(data);
      } else {
        preview(data);
      }
    } else if(data['action'] == 'move'){
      move(data);
    };
  });
};

server.js

var sys = require('sys'),
    http = require('http'),
    crypto = require('crypto');
    io = require('../'),
    server = http.createServer(),
    socket = io.listen(server),
    json = JSON.stringify,
    log = sys.puts;

server.listen(8000);

socket.on('connection', function(client){
  client.on('message', function(message){
    try {
      request = JSON.parse(message.replace('<', '&lt;').replace('>', '&gt;'));
    } catch (SyntaxError) {
      log('Invalid JSON:');
      log(message);
      return false;
    }

    if(request.action != 'close' && request.action != 'move' && request.action != 'speak') {
      log('Ivalid request:' + "\n" + message);
      return false;
    }

    if(request.action == 'speak') {
      request.email = crypto.createHash('md5').update(request.email).digest("hex");
      client.send(json(request));
    }
    
    request.id = client.sessionId
    client.broadcast(json(request));
  });

  client.on('disconnect', function(){
    client.broadcast(json({'id': client.sessionId, 'action': 'close'}));
  });
});

I'm intrigued by ratelimit()... If "last" value is calculated right away, then with every mousemove event the "last" will be updated? I'll have to read that a couple times to understand how it maintains the 40ms rate limit.

I apologize if I'm wrong, but I believe it should be "socket.broadcast(...)" as opposed to "client.broadcast(...)" (lines 33 and 37 in server.js).