The Debian installer team has published the second beta release of the installer for lenny (what will become Debian 5.0). I repacked the image for the Linksys NSLU2 with the proprietary IXP4xx microcode so Ethernet will work.
The installer is now available in two flavours for the ARM architecture: arm is the old ARM port whereas armel is the new ARM port using the EABI which offers better support for floating point and other features. Both the arm and armel architectures will be supported for lenny but the old arm port will be dropped after the release of lenny. At this point, I therefore recommend that people use armel for new installations.
The beta 2 installer image for NSLU2 can be found on slug-firmware.net.