So far the nicest solution I have found is one of the world’s smallest pocket routers TP Link WR703N.
Cheapest in price 25 USD, nice looking 5x5x2 cm plastic box, internal Wifi. Can be ordered on Ebay, shipping is free and it arrives from HongKong in a month. This router has a 400 MHz CPU, 4 MB flash (quite small), 32 MB RAM, 1 Ethernet, Wifi, 1 USB, 0.5 W power consumption. Powered via USB cable. Included power supply can be plugged in 110V or 220V.
It must be reflashed with OpenWRT Linux, where most necessary program modules exist, however not everything is compatible with Debian Linux. Can add USB hub, USB stick, USB sound card, bluetooth, webcam, 3G modem, 1-wire USB or serial module, connect to Arduino, set up Wifi client, place home webserver on router.
Comments