This will bridge the usb avr to the vhci-usb virtual usb host.

You'll need vhci-usb and vhci-usb-lib to build and use it.
(http://sourceforge.net/projects/usb-vhci/)

When setup, your avr project will connect to the linux usb system
as a real device.

BUILDING usb-vhci
-----------------
git://usb-vhci.git.sourceforge.net/gitroot/usb-vhci/vhci_hcd

The driver doesn't compile on recent linux kernels.
(commit 203800f0 Mon Apr 4)
0001-SPIN_LOCK_UNLOCKED-has-been-depreciated.patch
and
0002-need-transaction-translator.patch            
should fix that.

then simply "make && make install"

might need to copy the api header file:
mkdir -p /usr/local/include/linux
sudo cp usb-vhci.h /usr/local/include/linux


BUILDING libusb_vhci
--------------------
git://usb-vhci.git.sourceforge.net/gitroot/usb-vhci/libusb_vhci

This was a little more troublesome, but I didn't care to figure it out.
with libusb_vhci trunk (commit 5927f39a Sun Mar 27)

add
0001-Comment-out-function-that-doesn-t-compile.patch
patch to remove that won't compile (and we don't use)
then:
cd src
gcc -c libusb_vhci.c 
ar rcs libusb_vhci.a libusb_vhci.o
sudo cp libusb_vhci.a /usr/local/lib
mkdir -p /usr/local/include/linux
sudo cp libusb_vhci.h /usr/local/include/linux

Gives us what we need
