Python Internals: PyObject
Although it's been posted here (only twice, though!) before, Philip Guo put up a 10-hour series of lectures on CPython internals[0]. I am nearly done with them, and have found them very useful and well-paced. Posting here because the author of this article seems to have stopped the series, and anyone interested in this stuff should definitely check out the Guo lectures.[0]: http://pgbovine.net/cpython-internals.htm