I'm lucky enough that publishers occasionally send me free copies of books completely out of the blue. Last week I got possibly the most unexpected book I've ever recieved - a copy of the new edition of the Python Cookbook .
After scratching my head a bit, I remembered getting an email several months ago from the editor asking for my permission to credit me for a tip that they were using in the book. I was confused as to how anything I'd said could be of any use to a Python programmer, but after a fair amount of Googling I found what I was looking for.
It seems that a couple of years ago I got (briefly) involved in a discussion on the ActiveState Python board. They were discussing sorting algorithms and someone said that Python's "Decorate-Sort-Undecorate" (or DSU) method was very close to Perl's Schwartzian Transform. My sole input to the discussion was to point out that it was, in fact, closer to the Guttman-Rosler Transform.
And that's the fact that someone picked up on and thought would be useful enough to mention in the Python Cookbook. So there I am credited in recipe 5.2 on "Sorting a List of Strings Case-Insensitively" (along with Guido!) And that's why I got a free copy of the book.