I have managed to get my moschip-based ethernet dongle working, partially. Browser and default mail client work. GMail doesn't work (acknowledges network but won't fetch new mail), Market starts downloading apps but never finishes and GTalk doesn't even try.
Since I am not that familiar with the internal workings of linux, my solution consists of stuff I found on the net MacGyvered together with chewing gum and duct tape.
The short version (which may be useless - if you understand this stuff you probably don't need my help) is basically to build the kernel with these options enabled in the .config:
CONFIG_USB_NET_AX8817X (this is apparently needed even for non-asix devices)
CONFIG_USB_NET_MCS7830 (this is the moschip device)
Then install the kernel and reboot to host mode with the dongle plugged-in. After that, it's a matter of mucking about in a terminal using various combinations of
netcfg (Should show an entry for eth0. If there is no eth0, try dmesg to see if the dongle has been found on usb0 and is assigned eth0)
setprop net.dns1 192.168.0.1 (which is the IP of my router)
netcfg eth0 dhcp
I have begun writing a more detailed description, but I will be grateful for any helpful pointers* along the way, and if anyone knows how to get GMail, GTalk and market to work properly, I will be very happy indeed.
*except maybe suggesting that I buy a wifi router, as that would interfere terribly with the tinfoil hats of certain family members