i started a mongo client implementation in node.js, but it fell off my radar - the goal was to get it to work with mongoose, etc: https://github.com/JerrySievert/mongolike-client (it is not yet complete).

in the end, i just wrote my own database system, with a query language that could act as an intermediary from multiple sources (SQL, mongo, etc).

but, this stuff is mostly just for fun, my day job keeps me plenty busy.