Solution 1:

AVLD doesn't appear to be maintained anymore.

A similar video loopback package exists in the repositories which you can install - its called v4l2loopback-source.

Auto Install

First from a terminal, drop to a root shell

sudo su

If you havent installed kernel modules before with module-assistant run the following from a terminal

apt-get install module-assistant
m-a prepare
m-a update

Finally - download and install v4l2loopback

m-a a-i v4l2loopback
exit    

Manual Install

Download the package - once installed it can be found in /usr/src/v4l2loopback.tar.bz2

Copy the package to, for example your ~/Downloads folder compile and install

cd ~/Downloads
tar -xvf v4l2loopback.tar.bz2
cd modules/v4l2loopback
make
sudo make install
sudo modprobe v4l2loopback

This will create a /dev/video0 or /dev/video1 (etc) device.