it possible use a nodejs package inside meteor app?

Yes, it is possible. You can use an npm module in Meteor, since it's based on Node.js.

This code has worked for me fine, e.g.:

var fs = __meteor_bootstrap__.require('fs'); 

UPDATE: To install an npm module in a Meteor app

1. Inside your terminal, change path to your Meteor app directory.
2. > cd .meteor/local/build/server
3. Install an npm module like so > npm install module_name.

Edit: for anyone visiting this post, it is outdated. As of Meteor 0.6.4, you use Npm.require instead of __meteor_bootstrap__.require:

var fs = Npm.require('fs'); 

Also, if you don't use standard node package, but one from npm repositories, it's better to create a dependency so that it's automatically installed every time you create a new instance of the project. To do so, create a /packages/someName/package.js file with the following line:

Npm.depends({'packageName': 'packageVersion'});