Instructables is mainly a source of ideas for me. I get regular email updates from the site, but so far have not been tempted to try to build anything. The project that
@Bluejets linked to is waaay beyond my level of competence, but it sure looks like that guy is gonna have one happy son... that's assuming of course that his son actually gets to play with it!
I know my brother and I thought we were getting the best Christmas present EVER when a Lionel train set appeared under the tree one year. It was many years later, when Dad went into Valley Forge Army Hospital for tuberculosis treatment, that we finally were able to set it up in a partially finished attic of a rental house in Phoenixville, Pennsylvania. By that time, our father had purchased a bunch of accessories and a few locomotives and some rolling stock, so brother and I finally got to have a pretty good time with it while Dad recovered.
But... WOW! This Instructable makes our train set look pretty lame by comparison! A Star Wars toy that actually works!