gistfile1.js

var busboy = require('busboy');
var fs = require('fs');

app.post('/upload', function(req, res){
    var upload = new busboy({headers: req.headers});
    upload.on('file', function(field, file, filename){
        var gravar = fs.createWriteStream('/alguma/pasta/' + filename);
        gravar.on('end', function(){
            res.send('Upload terminado!'); 
        });
        
        file.pipe(gravar);
    });

    req.pipe(upload);
});