If you read the posting about the Sprite Sheet Exporter for Photoshop and was wondering about the same for Fireworks, wonder no more. Get your free sprite sheet for Fireworks here.
Follow the same instructions from the Photoshop extension but, instead go to Command->Sprite Sheet Exporter, when ready to generate your Fireworks file.
Hope you enjoy!
*Again, thanks for the great Aaron Beall for the support!