Intel maintains the iwl3945 driver. Their Linux driver project site is:

http://www.intellinuxwireless.org/

You can get the firmware for iwl3945 from:

http://www.intellinuxwireless.org/?p=iwlwifi&n=downloads

There is plenty of documentation for the iwl3945:

• iwl3945-base.c
• iwl-3945.c
• iwl-3945-commands.h
• iwl-3945-debug.h
• iwl-3945.h
• iwl-3945-hw.h
• iwl-3945-io.h
• iwl-3945-rs.c
• iwl-3945-rs.h
• iwl-helpers.h
• iwl-prph.h
• iwl-spectrum.h