Designing a PCB with a custom shape

Fritzing lets you design your PCB in any size and any shape. When you start working on a new sketch, a default rectangle board is placed in the PCB View. You can then define width and height in the Inspector or alternatively resize the board by dragging its corners.
To use boards with more complex shapes, create your board's shape with an external SVG editor (Inkscape, Illustrator etc.) and then import it to Fritzing. Follow these steps:

1. Design an SVG with two sub-layers:

• board layer with a path in any shape and size. The shape should be filled green and with no stroke.  NOTE: for gerber export, please use only polygons! any shape should work but there may be some aliasing, because some shapes go through a raster/vector conversion. 
• A silkscreen layer with a copy of the path you've just done, this time with no fill and with white stroke (for Inkscape users: stroke = 8 mil). Make sure the silkscreen layer is arranged at the top.

2. Illustrator Users: Align all elements to the center of the artwork
3. Illustrator Users: Use the crop tool and choose the preset "fit crop area to selected art"

4. Save the file as an SVG Tiny 1.2.

6. Drag a plain PCB to the PCB View.
7. In the Inspector, select "import shape" from the shape drop down menu, navigate to the SVG file and press "Open". Your custom PCB shape is ready to use!

You can inspect this sample shape to get a further sense of the details.  

Also, please note a potential "gotcha".  If you use Illustrator to make your custom board svg, and you notice that the board size is not correct in Fritzing, this is because Illustrator uses non-SVG-standard units for pixels.  In Illustrator-world, there are 72 pixels per inch, but the rest of the svg universe uses 90 per inch. Fritzing usually catches this, but if it doesn't, try the following: open up the svg in an text or xml editor and find the width and height attributes in the top level (<svg>) element, which will have units of "px".  Divide the value of the width and height attributes by 72, and replace the current attributes with that new number followed by "in".  For example, if you see width="100px" replace it with width="1.3889in".