Since in the Surge topic everyone seemed confused about what boosts what stat, I'm going to try to make a full list of them here. If I missed any or got them wrong, let me know.

STR = strength, INT = intelligence, DEX = dexterity, CON = constitution, CHA = charisma, SIZE = size

Skills:
-Geburah (Highmagic): +1 str
-Netzach (Highmagic): +1 cha
-Yellow (Lowmagic): +1 con
-Flex (Athletics): +2 str
-Penumbra (Night): +2 cha
-Drawdown (Moon): +1 int
-Nightkiss (Night): +1 int
-Stagform (Stag): +1 dex
-Crowform (Crow): +1 int
-Lichdom (Necromancy) +2 str/int at night, -1 str/int during day
-Bear (Totems): +1 str
-Fortuna (Rituals) +1 random
-Enlarge (Cosmic, Enchantable): +3 size
-Diminish (Cosmic, Enchantable): -3 size
-Populus (Rituals): +1 cha
-Weathering (Athletics): +1 con
-Dolphin (Astrology, usable on others): +/- 0-3 int depending on planets
-Skull (Astrology, usable on others): +/- 0-3 con depending on planets
-Antlers (Astrology, usable on others): +/- 0-3 dex depending on planets
-Lion (Astrology, usable on others): +/- 0-3 cha depending on planets

Karma Blessings:
-Knowledge: +2 int
-Beauty: +2 cha

Other:
-Throne: +2 cha
-Herofete: +1 all except size (does not stack w/ con/dex food)
-Favor/Strongfavor/Highfavor: +1 con
-Truefavour: +2 con, +1 all others
-Titan: +2 all
-Demigod: +3 all
-Evolution (Humans): +1 to a stat determined by class every 5 levels at 50+
-Con food: +1 con (does not stack w/ herofete)
-Dex food: +1 dex (does not stack w/ herofete)
-Shrink and Expand (Titans/Demigods): lower/raise size from 1-25

Fortuna is in Rituals.

Also, you forgot Populus, which gives a +1 to Cha. Also in Rituals.

Truefavours give +2 con and +1 to the rest don't they?

Crowform is +1 Int, not Dex. It pwns Stagform royally.

Edit: And yeah, True Favors are +2 Con, +1 everything else.

And.. normal Favor-High Favor is just +1 con

Athana's right, because all the levels of favor stack. Since Truefavor gives plus one to all stats, and regular favor gives +1 to con, it adds up to +2.

Ninja'd...

Herofate is +1 to all except size.
Food itself can be +1 dex and +1 const, but dont stack with herofate.

Enfeeble can be enchantable and cast on anyone and its -1 str. And it dont have cure for now.

Titans and demigods can adjust their size between 1 and 25 at cost of mana and willpower or endurance (forgot with one) and some time. So it cant be used in middle of fight.

Flex is +2 str, you are right.

And there also is weathering, +1 const.

Are you sure Herofete is +2?

Meh stupid me. Its +1 to all excpet size.

Oh ya infused food is +1 dex with infused cuisine, +1 con with infused gourmet items

Oh, and don't forget Astrology..

+/- 1-3 to the various stats.

Edit: And now i'm curious.. what happens to a human who doesn't have a class? Do they not get evolution?

I'm pretty sure Herofete affects size. It's been a while since I had one though.

Fixed/added all the rest, and I'm not including stat reducers (though the only ones I know of anyway are astrology, binah, and enfeeble).

EDIT: Fine!

Populus is Rituals.

No, it doesn't

Well, I guess I've got to trust the Athana.

All favours give +1 con from regular favours to highfavours. So favours, strongfavours, and highfavours.

I already said that

Well he didn't update it until I said it again.

I don't think Strongfavour gives you +1 con... it might, I'm not sure, I had one from Fain once...