Ryan, Reese's, and Ed's John Deere Snowmobiles - Also lots of great info including a Fire series manual

Andy's John Deere Snowmobiles

Tyler's John Deere Sleds

alt.snowmobiles.old - Old sleds newsgroup.

My posts to rec.sport.snowmobiles

Vintage Sleds.com - Very cool site. Check out the sled in the "Rare Birds" section with a 351 Windsor!

Central Snowmobile - Huge selection, free catalog.

Image Enterprises - Lots of parts, but pricey