Mineways is a program for exporting Minecraft models for 3D printing or rendering. The latest version works with Minecraft 1.2 and later (Anvil); Mineways Version 1.15 works with Minecraft 1.1 and earlier (McRegion). The home page is here. This page explains how to use Mineways effectively, with in-depth descriptions of the various options and related resources.
Current version is 3.06; for Mac, 3.05. With the free Mineways program you can interactively select a model from a Minecraft world map and have a 3D printing service make the model real. You don't need a 3D printer, and it's easy to upload and buy models - really! See the two-minute introductory video. Prices of 3D prints range from $5 to $500, depending on size. Or, just enjoy viewing and rendering your creation in a different way (but for rendering you should probably be using jmc2obj). Kids like it, too.