Hi there,
Here at Matrix, I do all of the e-block layouts for our curriculums etc. using CorelDraw (version 12, which is ancient!!) - which is really just a simple 2D vector drawing package. Pretty much any vector drawing package could achieve similar results - the most commonly used seems to be Adobe Illustrator; but like Corel, that is rather expensive. However, at home I use
Inkscape - it's totally free and open-source, does almost everything the expensive ones do, and personally, I actually find it much easier to use than CoreDrawl.
However, those are all 'graphic design' rather than CAD packages - for example, they don't have commands for adding a radius or fillet to corners etc. I use Corel just for compatibility with the files we already had when I started work here - because I learned engineering drawing with pencil and drawing board, I can get away without the convenience of those features if I have to.
Sketchup would be a good alternative if you want something a bit more suitable for engineering drawings - it isn't a true 'solid modeller' like SolidWorks, SpaceClaim etc., but it is incredibly simple to use compared to most other 3D packages, and the limitations of the free version are not a big deal for home use. In fact, you can duplicate almost every one of the "missing features" either with a little extra effort with the standard tools, or by installing one of the hundreds of free Sketchup plugins that are available.
With any of those packages, it is very easy to create a library of ready-made 'components' that you can just snap together to make complete layouts. We did consider making our own library available via the website, but unfortunately we need the server space for more important things, and it would cost us time to maintain that we just don't have at the moment. If that would interest anyone, let us know on the forum - maybe we could re-consider if there are enough people who would find it useful (no promises though!).
A little bit off-topic...
Almost every 3D System Panel component within Flowcode was designed using SketchUp - and we use it for designing many of our accessories, such as the plastic e-block covers. It's very well suited for making Flowcode components, as it creates models using triangulated faces rather than as true solids - which is exactly how Flowcode 3D meshes work. If you export an '.OBJ' file from Sketchup, it will import into Flowcode almost exactly as you designed it, including all of the colours and textures that you might have used. OBJ export is not part of the free version (it's a paid-for 'Pro' feature) - however, there is a free plugin you can use which works just as well. I've also found the community of users at the
SketchUcation forums to be just as considerate, generous and helpful as they are right here (I'm 'Trogluddite' if you want to say, hi!)
Disclaimer:
Note that the above opinions about the various bits of software are just from my personal experience. They are not Matrix "official endorsements" of any kind.