Travis looks like a fascinating CI system. It’s fully buzzword compliant (RabbitMQ, Chef, Vagrant, VeeWee), and provides a free CI service for open source projects.
The founders will offer private CI services in the future.
As running Continuous Integration is really expensive, they’ve made a call for donations. You can make a donation below, and you damn well should if your code (or code that you use) is built at Travis. Even if it doesn’t get compiled.