However, as of recently TP-Link – in Germany – is selling a consumer grade router device that's placed direct competition to the popular FRITZ!Box routers you can find in about 1/3rd of the households here.
Of course TP-Link doesn't specify on their product page, what and which amount of hardware this thing runs on. But… they do point you toward a source code download for GPL compliance, in other word, this thing definitely does run Linux.
My OS of choice would be NetBSD though…