Full disclosure: I am behind the operation of the site described here...
Circuits4Tracks has been started to provide affordable electronic solutions for model railroads.
This means that instead of simply offering a circuit for sale, you have a choice between building the circuit entirely by yourself (free circuit schematic, you do all the rest of the work), assembling your own components on a purchased circuit board, assembling the parts in a kit, or purchasing that fully assembled device.
At this time, the only product is a block occupancy detector, but free "tips and tricks" articles are being added.
For more information, see