If you know nothing about 3D printing start here:
What can you make with 3D Printers:
Thingiverse is an open online community supported by you, me and many other Makers. It is a great place to start for awesome ideas and FREE downloads!!! Just beware that some things work and some things require some a little more love and care before they become works of art.
CGTrader's site contains FREE 3D model downloads as well as 3D models for sale. If you have ever created a 3D model, you do it for the love of creating something new that you have made from scratch. But there are times when you do not need to reinvent the wheel, so to speak, and CGTrader has a lot of different RC Car wheel 3D models (both downloadable and printed) for a fair price and lot of other 3D models in many different categories.
If you are looking for a Company to create a 3D model for you:
CGTrader is a 3D model marketplace for computer graphics, 3D printing and virtual reality, backed by a strong professional designer community. On CGTrader, 3D artists, design studios and businesses share and sell their models. Enterprise and business customers can choose from a wide collection of high-quality 3D models or hire a designer for a custom job if the model needed cannot be found on the platform. (I am not affiliated nor do I receive remuneration for this advertisement...they just have a lot of awesome models.)
These are the machines that I built:
The machine on the left is a Reprap Prusa and the machine on the right is a Mendelmax 1.5 created using the Reprap Prusa!!!
They are good for making small to medium size prototype or real parts!
If you don't understand how they work; checkout this mistake!!!
The printhead (Extruder) extrudes hot ABS (Legos) or PLA plastic to form the part.
This is a brief video of a RepRAP Prusa printing (extruding) a Mendelmax 1.5 X-Axis motor mount. Yes, I have some more tuning to do in the software; the bridges drooped and there is a little over-shoot but the part is functional.