Got my first 3d printer on the way as we speak
I have been playing around this weekend with a few programs to create my own files and mess with others from thingverse etc
Google sketchup can export to STL only if you have the Pro version and download the extension
Tinkercad will export STL files and is very easy to use. Great to get started with but you will quickly find its limited features quite restrictive.
But I think this is all for a separate thread