Mongodb_pres is a project mainly written in Ruby, it's free.
MongoDB Presentation
http://www.mongodb.org/display/DOCS/Downloads
http://github.com/mongodb/mongo-ruby-driver
use this commit 1840c23364d9890cca0a331342414b2a1d2de69e, latest is broken (dccc442edb075bb5fdbc6f9d5bfdfb532ddb95f8)