LEGO might have started as a construction toy in 1949 but it has evolved into a precisely engineered medium for building static or dynamic models of all shapes and sizes. Currently I mainly use LEGO as an alternate to expensive model railroading, but it is an excellent medium for any sort of creation in three dimensions.
Relevant posts on this site are categorized under lego.
BrickShelf is a free image host for everything LEGO and practically an institution in the community. My account has pictures of almost all of the custom models I have designed and built since the mid 2000s. The majority of these models are grouped under space or trains.
Eurobricks is a LEGO community where I have written about most of my recent models. See my EB profile for a comprehensive list.