The iwl3945 driver is part of the iwlwifi project to provide support for the Intel PRO/Wireless 3945ABG Mini-PCI Express Adapter. The driver is included in recent kernels 2.6.24 and needs a binary firmware image, without which nothing will work, but nothing will complain, either.
For the firmware:
- Debian Sid: the package is firmware-iwlwifi. You will need to append non-free to the deb http://foo sid ... line in your /etc/apt/sources.list.
- Add /etc/modprobe.d/iwl3945-fix with the following content: "options cfg80211 ieee80211_regdom=EU". This will make channels 12 and 13 available. If an access point you know is there is not shown with "iwlist wlan0 scan" and you are in Europe, then this option may be missing.