I've been wondering if there are any other fan-made well-constructed campaigns out there that don't follow the GPC. Does anyone know of any?

For instance, I've considered using Pendragon to run a game in the early Italian Renaissance, or one following the Frankish invasion of Spain. Any ideas?

I don't know of any, but there are a few links to people's pendragon's campaign on the forum, where they have year by year accounts (not always diligently updated!).

We're running the GPC; but, in Hertford instead of Salisbury. We've only got a couple of years under our belts; but, there is a fair bit of info here:

http://hertfordshirekap5.wikidot.com/