The Freecom FSG3 is a small network-attached-storage box containing a PATA hard disk. The Freecom FSG-3 Storage Gateway does not have WLAN capabilities but the Freecom Storage Gateway WLAN does. The price difference between the two is often small. It has four USB 2.0 interfaces as well as external SATA interface.
We recommend running OpenWrt on the FSG-3. A tutorial can be found at http://www.openfsg.com/forum/viewtopic.php?p=22663#22663
Available in the US from http://www.mobileplanet.com/product.asp?code=129619 (broken link?) or direct from the freecom website http://www.freecom.com
OpenFSG site: http://www.openfsg.com (Forum and wiki)
OpenWrt Forum threads: http://forum.openwrt.org/viewtopic.php?id=5828
Dedicated feed: http://ipkg.nslu2-linux.org/feeds/optware/fsg3/cross/unstable/
Internal Photos: http://www.sukkamehulinko.romikselle.com/fsg3/
Recovery Process: http://www.openfsg.com/forum/viewtopic.php?t=1424
Some FSG's come with Marvell based mini-pci WLAN card. There's no source code for it on Freecom GPL package. Maxtor MSS-2 GPL source comes with 2.6 kernel Marvell WLAN driver. Looks like all you need is there. License on WLAN driver files say it's GPL. http://www.seagate.com/staticfiles/maxtor/en_us/downloads/MSSII_3.1.2.src.tgz (Warning, 100MB file)
CON401 is for serial port and documented at http://www.openfsg.com/images/0/0f/FSG_RS232Adapter.pdf
Some other ports are documented here:
CON200 seems to be for fifth USB port and pin-out is likely same as others so that's easy.
CON701 is a secondary SATA port.
CON400 secondary serial port
CON301 fourth lan port
JTAG100 is JTAG
Verified that CON701 is SATA port. Same pinout as CON700.
Temperature and fan control details (http://www.winbond.com/PDF/sheet/w83782d.pdf) at http://www.openfsg.com/forum/viewtopic.php?p=10686#10686