Debian has a great package management system and includes thousands of packages for many architectures. OpenWrt has great Linux kernel support for many embedded devices. Bringing these two strengths together opens a whole new world of possibilities. It is greatly underestimated what these embedded devices are capable of.
Running Debian on these devices can turn it into something more than it was supposed to be. It is just one apt-get install away.
For more an overview of supported hardware, installation and usage instructions see the DebWrt development Trac part of this site.