This appears to leak something in Node.js 0.10.10. Requires the `heapdump` module, `npm install heapdump`.

check.js

var fs = require('fs');

var files = fs.readdirSync(__dirname).sort();

for(var fileOn = 0; fileOn < files.length; fileOn++) {
  if (files[fileOn].indexOf('heapsnapshot') > -1) {
    if (isLeaking(files[fileOn])) {
      console.log('Still leaking.');
    } else {
      console.log('NOT leaking?');
    }
  }
}

function isLeaking(heapFile) {
  var heap = JSON.parse(fs.readFileSync(heapFile, {encoding: 'utf8'}));
  
  var nodes = heap['nodes'],
      numNodes = nodes.length / 5,
      largeNodes = [];
  for (var nodeIndex = 0; nodeIndex < numNodes; nodeIndex++) {
    if (nodes[nodeIndex*5 + 4] > 5000) {
      console.log('Node '+nodeIndex+' has '+nodes[nodeIndex*5 + 4]+
        ' references, and is a '+heap['strings'][nodes[nodeIndex*5 + 1]]+'.');
      largeNodes.push(nodeIndex);
    }
  }
  
  return (largeNodes.length > 0);
}

run.sh

#!/bin/sh

rm -f heapdump-*
node --expose-gc server.js &
sleep 1
ab -n 10050 -c 100 http://localhost:3463/
kill -USR2 `cat pid`
sleep 1
kill `cat pid`
node check.js

server.js

var http = require('http');

var heapdump = require('heapdump'),
    fs = require('fs');

var server = http.createServer(function (req, res) {
  res.end('hi');
  global.gc();
});

server.listen(3463);
fs.writeFileSync('pid', process.pid);