I have an application that uses the node twit module that is available via
npm install twit
I deployed the node module locally from .m
This code worked for me with meteor 0.8.x and node_modules being installed in ./public of my app:
var path = Npm.require('path')
var fs = Npm.require('fs')
var base = path.resolve('.')
var isBundle = fs.existsSync(base + '/bundle')
var modulePath = base + (isBundle ? '/bundle/static' : '/../client/app') + '/node_modules/'
var twit = Npm.require(modulePath+'rssparser')
It may also be a good idea to create packages.json file within ./public for easier updates/installs through npm.
Long live Meteor!