SketchUp
SketchUp is a 3D modeling computer program for a broad range of drawing and design applications.
For anything spatial or architectural, where exact measurements are needed to create your model, SketchUp is a great tool to use.
Supported filetypes
STL (best for 3D printing), DAE ,SKP, DWG, DXF, JPG + PNG (for textures and images)
Minimum system requirements
At least 4GB of RAM. At least 700 MB of available hard-disk space. Intel HD or similar graphics card with at least 512 MB video memory