Here are a few links that I have found, I have them listed in these catagories: references, parts, and enthusiast homepages. If your site is listed here and should not be here, let me know. Likewise, if you think your site should here, let em know.
Mirafiori.com - an amazing Fiat/Lancia/Yugo resource, check out the Forum!
Fiat Central - A budding resource with a forum and plenty of Fiat 500/600/850 info
Viva Lancia - this site is devoted to anything and everything Lancia
The Fiat World - Links to sites of nearly every type of Fiat built
These are some Fiat and/or Lancia parts places that cna be found online. I have not used all of them, so a link to them on my site does not mean I endorse any vendor in particular.
European - Appalacian Performance