Where can I find a good Civilization 4 Strategy guide?

I would recommend Civ Fanatics. As a bonus, they've got information on Civ III and Civ V as well.

Here's a direct link to their strategy section: http://www.civfanatics.com/civ4/strategy

I use GameFaqs for all of my FAQ needs. Here is a link to the generic Civ4 listing, but they have FAQs specific to each edition, goty etc, as well.