Ever wanted an accurate 3D model of your favorite molecule? Here's how. All the software used is free, and there are lots of ways to fabricate your model. I used a 3D printer to make small molecules and a laser cutter to make larger versions.
To generate a 3D model, you will first need the molecular structure. These are usually determined using X-ray crystallography, and there are internet repositories of these containing hundreds of thousands of structures. Most well known is the Cambridge Structural Database (CSD), and I used their program Mercury to produce the .stl file needed for printing. But before you do that, you will need a file readable by Mercury. Crystal structure files have standardized around the crystallographic information file (CIF) format. Your best bet here (if you do not have a licence to the CSD, like most people) is the Crystallography Open Database. It is open access and searchable in various ways, most intuitively using the JSME editor, which allows you to input a molecular structure by drawing it. This presupposes you know something about chemical shorthand, wherein lines indicate C-C bonds and hydrogens are assumed to be filling the valency of C if nothing else is drawn. The example above shows what you'd draw if you want to find ethanol.
However, if it is a common molecule you're after, even this might be overkill: just try searching for e.g. "ethanol.cif" or "caffeine.cif", and you might get to go straight to what you're looking for. However you find it, once you have the cif file of the molecule you're interested in, save it to your computer and move to the next step.