You'll find here my experiments with my Asus WL-HDD2.5.

The WL-HDD2.5 is a tiny file server with 802.11g wifi. Its main features are

Linux based, with all source and free SDK available
133 Mhz MIPS processor, 16 MB Ram, 4 MB flash
one USB 1.1 port, one 10/100 ethernet interface, and 802.11g WIFI support
one 2"5 IDE ATA100 hard disk can be plugged in
Tons of alternative firmwares available like OpenWRT
Low price. Got it on Ebay for 35 euros !

Completed Projects

Installing OpenWRT

OpenWRT can be installed easily folllowing the instructions available on their web site. The Linux/TFTP method didn't work for me, but running the Asus firware tool (RescueR.exe) under Wine worked (if someone is interested I have a pcap trace of the firmware upload).
Once installed, you'll have 2000KB of JFFS2 storage free to customize your toy. To have the ATA and USB interfaces working, you'll need to install the folling packages: kmod-ide kmod-usb-core kmod-usb-ohci kmod-usb-storage. But I had to modify /etc/modules.d/20-ide, like this : (i.e. pdc* loaded after ide-core)

# cat /etc/modules.d/20-ide 
ide-core
pdc202xx_old
ide-detect
ide-disk

To use the battery saved internal clock, install this module and se the clock using this utility. mknod /dev/rtc c 12 0

The Exim binary compiled for my WRT54gs also works under the WL-HDD. So if you need a small and fast MTA with anti-spam features, give it a try!

Kismet works also (with source=wrt54g,eth2:prism0,foo).

Nbench gave me an integer score of 0.898, so it's 50% slower than the WRT54.

Projects not yet completed

Debian mipsel in a chroot

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Completed Projects

Installing OpenWRT

Projects not yet completed

Debian mipsel in a chroot

Serial port

2nd USB port