Roving networks (
www.rovingnetworks.com) wifi modules (RN131, RN171 etc) run lwip 1.3.0 from the ROM and is 802.11 b and g. You can run applications directly on the chip - although the architecture is a little strange and probably under resourced. It is possible to load applications from the built in serial flash, which makes it possible to divide and conquer, but it can take some getting used to.
It is the lowest powered wifi chip in the world and can be used for battery wireless sensor apps as well as a general purpose wifi device. We use it in the home automation space very successfully, and I know many otehr applications from streaming audio devices to thermostats...
Hope that helps,