gconftool-2 --all-dirs /system/networking/wireless/networks
If you want to delete one, do
gconftool-2 --recursive-unset /system/networking/wireless/networks/BADNETWORKNAME
I find this useful when I'm in a venue, such as a tech conference, where there is both a free conference wireless network, and a paid wireless network run by the convention center. If you ever accidentally associate with the paid network, then whenever the signal strength of the paid network is higher, NetworkManager will prefer it to the free one. The fix is to delete the paid network data from the gconf database.