PrimaGames make their own strategy guide books and seem to be letting some their strat guides be used online for free along with other things like cheats and demos.
GameFaqs and The-Spoilers have strategy guides for alot of the games around.
Sony makes the Playstation systems and alot of their games so they also have the playstation underground online.
PlayOnline was created by squaresoft for their Final Fantasy series and proboly has guides along with other things for their other games
Bradygames make their own strategy guides like Prima but they don't give much away for free on their site a small selection of cheats and some updates to their strategy guide books not the entire updated guide though
If you have any strategy guides or sites for them you know about post on the message board where to get to them and I'll link them here.