A Mesh built of re-used WLAN-routers.

If you have a big house or even a hostel for many people and
are environmentally aware, a MESH from re-used routers might be the right thing for you.

background knowledge:

The routers should be interconnected by cable for best performance.
This is also true for "new" devices, since the advertised 5GHz backbone is still the bottleneck in your mesh.
With the help of B.A.T.M.A.N. (Better Approach To Mobile Adhoc Networking) the devices form a distributed switch.
Each device thinks it is directly connected to the other.

You can either buy the recycled devices here, or get them yourself and
I only do the configuration.

If you're interested or have more questions about a MESH using openwrt, do not hesitate to contact me for more information