While ARM is a very important platform, support for it in Debian has faced a number of problems recently: there was no developer accessible machine for a long time (they're two now), buildds sometimes have a hard time keeping up, etc. Most importantly, there are not enough people actively involved in the ARM port. We need more people doing debian-installer and kernel work, and track other ARM related issues.
One reason why few people are working on ARM is probably the lack of a cheap platform that can be used for development. Fortunately, this problem has now been addressed. Over the last few months, I worked (in collaboration of the NSLU2-Linux project) on debian-installer support for the Linksys NSLU2, a sub $100 device with 32 MB RAM, Ethernet (which unfortunately needs a non-free driver) and two USB ports. You can attach a USB disk and run a full Debian system on this device.
While there have been some instructions on the web about how to get Debian going on the NSLU2, basic support for the device is now included in debian-installer. In other words, you can do a user-friendly installation and it will just work. Here are instructions.
In the future, the NSLU2-Linux people and I will add more support for other ARM based consumer devices, such as Network Attached Storage (NAS) devices (basically a hard drive with a CPU/RAM and Ethernet, sometimes also including wireless; in other words, a perfect platform for Debian).
On a related note, I'm also working on getting debian-installer going on a number of MIPS based consumer devices, such as the Netgear WGT634U wireless router. However, this work has not reached the maturity of NSLU2 support yet. There is a status overview and TODO list.