If you can find an old Linksys, they are nearly bullet proof. They most likely only support 802.11b/g, but that is probably faster than your internet connection anyway, so you will never know the difference. I have a Linksys WRT54G which sits on a top shelf on the second floor of the house and it will easily provide coverage to a 200' - 250' radius around the house. I have never done any actual tests, but I know the lounge in the riding arena is right around 200' from the station, and people connect from there all the time.
I
never have to perform a reboot on my router to get it to work right.
This model is still very
actively bought and sold on e-bay.
edit: A lot of those listed in my e-bay link are some sort of special T-Mobile version. I DO NOT have this version, and I have no idea if it is the same internal guts. I can assure you it is not the same internal software as mine, so it probably works differently.