This is simple nautilus script here.
I record most in gtk-recordmydesktop and this program saves my films in .ogv format. I wanted to create some easy way to convert my films to .avi format and I made this script for my own use, but I wanna share it with you.
This version of script will convert your .ogv file to .avi (or other) using lavc (video codec) and mp3lame (audio codec). If you will like it I can upload a version where you will be able to type your own kind of codecs.