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 with 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.