// I've updated the list since a couple of tools aren't available anymore.

There are a couple of hosted continuous integration tools:

• circleci.com (no free OSS builds)
• cisimple.com (mobile only) **shutdown on sept 1, 2013
• http://codeship.com
  
• drone.io
• semaphoreapp.com
• tddium.com
• wercker.com (also free for privates while in beta)

Disclaimer: I'm one of the cofounder of codeship.com. We also offer a hosted CI & CD solution.