> Can you name a few major projects, preferably on the same kind of scale as the examples that have been mentioned in other posts in this discussion, that were built using TDD?

Operating systems? No. Sorry. Operating systems, as a rule, predate modern practices by some 1-4 decades. Making a kernel like Linux, Darwin, or FreeBSD testable would be a task somewhere between "massive headache" and "really massive headache". I've done some in-kernel unit testing, but only on our own driver subsystems that could be abstracted from the difficult-to-test underlying monolithic code base.

Outside of kernels/operating systems, just Google. Unit/automated testing is prevalent in just about all modern OSS software ecosystems.

A few examples, off the top of my head.

Apache APR: http://svn.apache.org/viewvc/apr/apr/trunk/test/README?revis...

Clang: http://llvm.org/svn/llvm-project/cfe/trunk/test/

Go: https://code.google.com/p/go/source/browse/src/pkg/math/all_... (see all *_test.go files)