pkgcloud (GitHub: nodejitsu / pkgcloud, License: MIT, npm: pkgcloud) from Nodejitsu is a module for scripting interactions with cloud service providers. It supports various services from Joyent, Microsoft, Rackspace, and several database providers like MongoHQ and RedisToGo. The authors have attempted to unify the vocabulary used by each provider -- for example, pkgcloud uses the term 'Server' to refer to Joyent's "machines" and Amazon's "instances".
Services can be introspected and resources can be fetched. The API is naturally asynchronous, with callback arguments using the standard error-first pattern.
The roadmap promises support for more services in the future, including CDN and DNS.
rewire (License: MIT, npm: rewire by Johannes Ewald is a dependency injection implementation that can be used to inject mocks into other modules and access private variables.
As an example, consider a module within your project that uses the standard fs module to read a file. When writing tests for this module, it would be entirely possible to use rewire to modify the fs module to mock the readFile method:
Notice that rewire was used instead of require -- rewire itself works by appending special getters and setters to modules rather than using an eval-based solution.
It supports several authentication methods, including keys, bidirectional port forwarding, execution of remote commands, interactive sessions, and SFTP. Brian has provided some detailed examples of how to use the library's event-based API.