I've been working on shoehorning FreeBSD-current onto the RouterStation Pro. It's a rather cheap but nice Atheros MIPS board by Ubiquity. It was tricky, but doable. I now have a cut down kernel and memory root filesystem stored on the on-board flash - enough to run it as a basic access point.
FreeBSD-current has support for the chipset - it's the AR71XX kernel config file. I've added a few more devices (USB, disk, MSDOS, redboot) to the default kernel. The default cross-build system works just fine.
I've been using TFTP loaded kernel+mdroot images to test out standalone functionality, along with TFTP + NFS root images to run a mostly-full development environment.
The board uses RedBoot as a bootloader. There's a tool by Ubiquity which generates firmware images which are understood by the bootloader and will overwrite the non-system area of the on-board flash. This makes dumping an image onto the system highly trivial. The bootloader can also boot the (uncompresed) kernel+mdroot images via TFTP as well as having a compressed version written to flash - so I can easily test the standalone images without constant re-flashing.
RedBoot makes it easy to TFTP upload a replacement flash image written out by the Ubiquity tool. It takes care of erasing, repartitioning and copying into the onboard flash without overwriting or damaging the RedBoot code, flash partition and configuration areas.
There was a bug with the PCI probe code until a couple of days ago where PCI cards (ie, stuff like the mini-PCI radio cards!) wouldn't be enumerated unless bootverbose was specified. Gonzo traced it down to a missing DELAY() - Linux was waiting a lot longer between probes than FreeBSD was. PCI devices now probe and attach correctly.
The geom_redboot module doesn't attach to the on-board flash (device "spi") - it only probes "cfi" flash devices. A quick patch to src/sys/geom/geom_redboot.c to also probe flash/spi has fixed this. I've asked Gonzo/Warner to investigate this and possibly commit a fix. With this in place, FreeBSD can mount a compressed, read-only filesystem from the "rootfs" flash slice rather than needing to pack a kernel+mdroot into the kernel flash slice.
So far, so good. I've written out a basic image that can be coaxed to be an open (no authentication) access point.
Instructions on re-flashing the unit (but it doesn't mention that the reset button must be held down during power on!): http://www.usualcoding.eu/post/2010/01/15/Flash-OpenWRT-on-the-Ubiquiti-RouterStation-Pro
My FreeBSD router-station pro wiki: http://wiki.freebsd.org/AdrianChadd/UbiquityRouterstationPro
My work-in-progress tarball of "stuff" for building firmware images for the RouterStation Pro: http://people.freebsd.org/~adrian/rspro/