Scott Guthrie has returned to blogging with a tremendous piece on his team's effort towards reaching "ZBB" or Zero Bug Bounce.
I've personally never worked on software project as large as the ASP.NET 2.0 project, so it's fascinating for me to read Scott's description of the testing and check-in process. Typically, my check-in process is to get latest on any files I didn't change, build, and run my unit tests. Assuming everything passes, I check in my files, get latest again build, and run the the unit tests again. If everything still passes, I'm done with the check-in. If all went smoothly, it's all done under half an hour.
For the ASP.NET team, every check-in undergoes peer review and is run through a few hours of checkin test suites. They then run more exhaustive nightly tests over the product to catch issues in the latest builds. That's pretty impressive.