Interesting Things
If you're using ack in project for textmate, be sure to edit your .ackrc file to include any non-standard file types you're using.
A project had a dramatic speed up in their test suite by mocking out ActionMailer in tests. Something to consider if your tests cause a lot of email side effects.
field_named wasn't working for us when using Webrat to drive Selenium. Our fork with the simple fix can be found here.