Probability that mangles the mind

Here's an impressive blog entry about "recreational mathematics", in the area of probability:
http://brianclegg.blogspot.com/2010/05/probability-that-mangles-mind.html
Briefly, someone asks: I have two children. One is a boy born on a Tuesday. What is the probability I have two boys?

The answer is not 50 %.

This is even more mind-boggling than the Monty Hall problem, a variation of which I published in the web about 14 years ago:
http://www.pcuf.fi/%7Epjt/problem/p-04-p-e.html