The 3D printer is from Builda3DPrinter, a Dutch company (actually just one guy living in Hardinxveld) that sells kits and supplies for delta printers. There's lots more to say about the robot and how it works, but as a hobby, 3D printing is an interesting mix of getting the machine to work well and coming up with cool things to print. I'll just say a bit about it below.
The printer is basically a computer-controlled glue gun: you feed it plastic filament, it melts the plastic and squeezes it through a nozzle onto where you want your object to be. There are a few plastics you can use, in a modest range of colours, but you're very constrained in the materials you can work with and the properties they can have. On the other hand, complicated shapes are easy, with a few constraints. The main one is that the plastic of each layer needs something to support it until it cools. For a modest overhang, the layer below will do fine; if the plastic needs to jump a gap, you can try going fast and blowing a fan in hopes that it cools before it sags too far, but for some shapes you really need to print plastic supports. You print them intentionally very weak, and they can usually be removed without too much suffering, but really, it's much easier to print objects that don't have too much in the way of overhangs. Beyond that, though, and a certain limit on the size of features imposed by the 0.4mm nozzle, you're pretty free to make complicated shapes.
So far I've printed a range of things: cute figurines, fiddle toys, neat math, classical art, astronomical things, and mechanical parts. Several of this last category have been upgrades to Coral itself; the machine comes out of the RepRap project, which aims to open 3D printing to hobbyists by designing printers that are made out of off-the-shelf hardware and parts they can print themselves. As with open-source software, it's easy to grab someone else's parts, modify them, and print them. It must be said, though, that the ecosystem is less like the (relatively) orderly world of Ubuntu packages and more like the weed-strewn garden of scientific codes: you can probably find some brilliant parts on the website of some enthusiast, but they're not necessarily designed to work with anything else.
Fortunately, the main consumable is filament, which costs about 3 (Euro) cents a gram. And you can make a lot of little plastic whatzits out of a kilogram of plastic. So it actually makes sense to print rough drafts of objects. This is also good, because the printer is a little finicky, sometimes requiring rather specific settings to work.
When the printer is working, though, I can print lots of neat objects with little work on my part. So it makes sense to give them away to people who like them or just think 3D printing is cool. In exchange, I've asked coworkers and friends for neat 3D things they'd like to see printed. I encourage you all to offer suggestions too!