Bug#501801: lenny beta2 install on Lenovo ThinkPad T61 without troubles
The driver is in the kernel but you also need to install
firmware-iwlwifi from non-free.
I installed Lenny on my T-61 using an ISO downloaded around November 10.
The installer did prompt me to provide a firmware file but did not
inform me that a package was available or offer to enable non-free in
order to install it during installation. After installing
firmware-iwlwifi, wireless worked fine for me.