while messing with a neighbours open wireless i found a handy trick.
in the routers settings (usually found at 192.168.1.1 while connected), you can choose to backup settings which will download a config file of some sort to later upload if things go wrong....in this case "user.conf"
after a week of using their wireless they must of got the idea something wasn't quite right and the router was going slower,
they only did half a job however, the wireless was still wide open yet access to router settings at the above address was now passworded, so out of interrest i pointed back to the address 192.168.1.1,,, "please insert username and password"
i then tryed 192.168.1.1/user.conf
TADA!!,, the config file downloaded with no need for a password, upon opening a quick readthru gave me the username and password.
this was with a BelkinGPlus, i'm unsure what other routers this would work with...