The LinksysUSB100MLinux is a page describing the Linksys USB100M Compact USB 10/100 Ethernet Adapter, and running it under Linux. It does work under Linux properly. Using the RTL8150 module.
# modprobe rtl8150
In your kernel compile .config you will need to have:
CONFIG_USB_RTL8150=m
Also, RTL8150 is not in the standard 2.4.18 Linux Kernel. You will need to use a newer kernel or patch your kernel to get the RTL8150 module. I'm using 2.4.19-pre10. The RTL8150 module is included in 2.4.19
After you have inserted your module, you should be able to do an:
# ifconfig -a
and see an eth0 to dhcp an address
# dhclient eth0
The Linksys USB100M is not a Pegasus chip, so don't try to load that driver for this USB NIC.