node-mongodb-driver
(the underlying layer that every mongoDB client uses in nodejs) except the cursor API that others mentioned has a nice stream API (#458). Unfortunately i did not find it documented elsewhere.
Update: there are docs.
It can be used like this:
var stream = collection.find().stream()
stream.on('error', function (err) {
console.error(err)
})
stream.on('data', function (doc) {
console.log(doc)
})
It actually implements the ReadableStream interface, so it has all the goodies (pause/resume etc)