Where can I find the information one would get in a favored soul handbook? My google fu has turned up no such page, so I'm curious.
However, there are a number of useful divine resources out there.
Favored souls are best thought of as sorcerer clerics.
The most tricky aspect of the soul is the spell list. Their problem is the exact inverse of the archivist but can be selected for in the same way. They also share many commonalities with the spirit shaman.
Therefore, we look at the Spirit Shaman Handbook, the Cleric Handbook, and the Archivist handbook for inspiration. We also can dig around a few of the favored soul specific threads for advice (here, and here). As well as the official wizards discussion here.
As such, we can reconstruct a handbook of sorts in this answer.
The first question
Are you positive you want to play a favored soul?
The FS is considered to be a extremely "meh" class in direct competition with a Tier 1 class. There are some excellent reasons for being one, not least the fact that you can enjoy the company of a much lower tiered party than the cleric without needing to "dumb down" your optimization. It may also fit the flavour of your requirements better.
MAD MAD all the way. (Multiple Attribute Dependancy)
Charisma is your casting stat according to this OGL reproduction of the class. But wisdom is your DC basis. Plan your spells carefully to see which stat requires emphasis and which stat requires minor magical buffs.
Given how poor this class appears in performance, this article to the contrary, you may want to ask your DM to make the class based off one casting score. If he requires you to trade in your class features to do so, immediately take him up on his offer.
Other stats are less critical, and should be shaped with the rest of your build in mind.
I say it three times: Thou shalt not give up caster levels. Thou shalt not give up caster levels. Thou shalt not give up caster levels.
Level adjustments are nice, but if you want level adjustments, go find yourself a shiny stick and beat people with it. You need caster levels.
With that said, here are some of the more interesting races from the master race list. If you can get away with buying LA for experience, especially with level adjusted experience rewards, enjoy yourself here.
As per here:
I say it three times: grow your spell list, grow your spell list, grow your spell list. No, really.
However, if you're not going to focus on that, this summary works well:
Looking through here we get:
The "X theurge" (mystic, eldritch) route. One advantage of charisma as a casting stat is that it synergizes very very well with charisma based arcane classes. Using precocious apprentice, a Sorcerer 1/Favored Soul 4 will get you into mystic theurge early and will allow you to spam spells all day long.
Alienist/summoner/malconvoker/fiendbinder/Master of Shrouds: You can spam spells. Summoning is one of the better spam routes. Take advantage of it. The fiendbinder is fascinating because a number of cleric spells allow for insane skill buffs. Take advantage of them.
Fochlucan Lyrist: If you can jump through the hoops, the Cha of your class may reduce MAD slightly.
Shadowbane Stalker: some sneak attack to go with your casting.
Church Inquisitor, Contemplative, Divine Oracle, Singer of Concordance, Divine Disciple, Dracolyte all offer bonus domains and good PrCs to boot.
Seeker of the Misty Isle, for something different.
Dweomerkeeper requires special mention, as it grants arcane access. Spelldancer for the metamagic cheese.
Sapphire Heirarch for gishy builds.
Anima Mage, if you can adapt it for clerics synergizes well with your Cha.
See here for details on the shadowcraft mage.
Getting access to the spell domain and "anyspell" is also extremely worthwhile, as you can remarkably broaden your spell list with arcane spells.
Raptoran and skypledged (you'll need to dip something else to get the appropriate summon) for some interesting air flavour.
Any from here to expand your spell list.
Fiddly, but awesome: War Weaver (though the build cited there seems to be headache inducing), Spellguard of Silverymoon.
Getting access to domains should be fairly high on your priority list.
If you can get access to plant, Holt Warden is quite competitive. Access to war for ordained champion
As per cleric, really.
Build your spells as versatile as possible, as per here. Decide on your party role (and may the gods have mercy on your soul if that's heal battery.) Enjoy.