I just found Voivod's official fan site (link) and there is an amazing amount of live and demo material available for download. Demos from Hatross and Negatron were just added to the site. I haven't gotten around to listening to these demos as I have had the demos from Nothingface on my iPod for the last week.

For anyone who is a fan of Voivod or thrash in general, this site is a great find.

Links:
Voivod Main Site (link)