Here are a few free stock-footage places.

Footage Firm is in the business of selling stock footage, but has free stock footage giveaways monthly (I think) if you register...
http://www.footagefirm.com/freeclips.asp

This site is part of the Footage Firm:
http://stockfootageforfree.com/

Look around Detonation Films as well -- not sure what kind of fire you want (Detonation Films is mostly explosions and rockets and such)
http://www.detonationfilms.com/free_stuff_page_2.htm

Tim L