This should all be in electrical/design/. There should be a folder for each board, containing the datasheets for the parts on the board. There should be PADS drawings, and PDFs of both the schematic and the layout, and a text file BOM. There should be an explanation of what the board does, and a list of the commercial parts that it connects to. If there is a good way of linking to the datasheets for these parts, then we might do that as well.
Parts that aren't custom built (motors, sensors, motor controllers, etc) should be in documents. These will be further organized by folder.
Things aren't all where they should be, and often there's three places to look for something. We're working on that. However, I don't intend to touch the mechanical folder.