I'm a huge fan of these and love all the different ways they use to move around the LEGO basketballs and footballs (soccer balls). The idea is that as long as there is a predefined 'entry' point and 'exit' point for the balls, people from different areas (cities even countries) can build their machines and then bring them all together in one location and make it work (with a bit of tweaking)
This gathering has 93 modules in total (apparently a world record) and was on display at LEGOWorld Copenhagen 2011. Whilst the majority of modules us PowerFunctions or the older train sets to move the balls, I did spot a few NXT's in the mix. It's a long video, but well worth the watch, especially if, like me, you're interested in all different types of LEGO mechanisms.