The CakePHP MongoDB plugin. Include the plugin, create a model, flag it to be sent to Mongo, and boom, your'e in business. Simple, elegant.
Useful intro to using MongoDB with CakePHP. Works quite nicely, load the plugin, specify your model should use Mongo, and boom, you're in business.
Scripts to auto install node.js on Ubuntu. Includes a few handy dependencies, etc. Neat.
Cube is an open-source system for visualizing time series data, built on MongoDB, Node and D3.
Interesting article on how webpop built their infrastructure on Rackspace's cloud. Includes links to a few useful tools (chef, wormly, new relic, nagios, ganglia, and others).