I started designing in 3D at home something like ten years ago, and there were very few 3D packages that were within the price range of the hobbyist. I was wanting to design rolling stock and scenery for Microsoft Train Simulator and was introduced to a package that at that time was called 3DCanvas. This package was produced by a gentleman in Canada, trading through his website http://www.amabilis.com
3DCanvas was available in three versions, a freeware feature restricted version, and two payware versions, Plus and Pro priced at around $35 and $70 respectively. The payware versions had plugins to import and export from and to a range of file formats, and a member of the train simulator community created plugins to easily create steam loco motions, etc.
During the life of the program, the program author has continually developed and improved the software, and it is currently available under a new name of 3DCrafter. The name had to be changed due to a trade name dispute.
3DCrafter, despite being an inexpensive package, has quite a lot of features and I find it extremely easy to use. I've tried Sketchup in is evolving guises over the years and don't like it's "mickey mouse" feel. I've also tried Blender.....but I find it awful....and found that I needed to memorise loads of key combinations...or have a sheet of paper with them written on...to be able to do anything. 3DCrafter's gui has all tools and commands available to use by mouse clicks.
There is a but...there has to be!!....with 3DCrafter. It does have a few issues. Boolean operations don't work all that well, and you need to do a bit of cleaning up of the merged shape after some operations. And for 3d printing, the standard exporter for .stl files does not work properly......but there is an alternate .stl file exporter that is freely available that does the job. And the final part of the but...is that due to the Boolean operators being iffy, finished models can end up as multiple meshes - which can cause issues with slicing software....but having said that, I never had a model refused by Shapeways due to multiple meshes.
And for a final point, to get a flavour of what 3DC looks like, take a look at my build thread for a Pobjoy engine I created for a plane for FSX.http://forums.uktrainsim.com/viewtopic.php?f=18&t=88248&p=1065524&hilit=pobjoy#p1065524
And you could even try 3DC out for free by downloading the freeware version. You can create models but save in any other form than 3DCs own format.