Today I've found one very interesting GoogleTechTalk presented by one of the authors of
Java Puzzlers book.
I, personally, not a professional Java programmer and would not watch it if I noticed the full title :-) . But it was still very interesting and fun for me, and, besides, some of the situaltions you can meet in C/C++ also.
So, if you want to know that Math.abs() may sometimes return negative values and many other not_so_evident things -
check this talk out