Blessings

Akatosh: When you've finished the quest Dragonslayer, Akatosh's Blessing gives you: 50 Magicka Regeneration, Fortify Health, Stamina, Magicka by 100.

Arkay: Fortify Health by 25, 75 regenerate magicka if you've read 75 or more books, Fortify Health 75 (additive) if you've killed 250 or more undead.

Dibella: Fortify Persuasion (dialogue speech checks) +10, +15 Barter if you have Agent of Dibella.

Julianos: Fortify Magicka +25, +50 more if your Magicka is at or above 400 base, +25 more if you've read 100 books.

Kynareth: If you've not used the stolen Eldergleam sap to repair the Gildergreen, Fortify Stamina +25. Additionally, if you bring the sapling to grow into a new Gildergreen for Danica Pure-Spring, +25 more. Cure Disease also requires you not to repair the Gildergreen.

Mara: Fortify Restoration +10, +50 Health if you have Agent of Mara.

Stendarr: +10 protection from lifedrain, if you're not a werewolf, vampire, and if your Conjuration is below 31 (not equal or less than, only less than) Cure Disease also has this requirement. In addition, if you've killed 50 or more daedra, +50 Fortify Health.

Talos: Must not have joined the legion ("Joining The Legion" must not be complete) must not have killed Paarthurnax (It's coded as 'less than' killing him, so finishing it with a choice mod will probably also count as killing him either way) and must not have taken Ogmund's Amulent and returned it to Ondolemar (Search and Seizure must not be completed) if these are met (in addition to the universal rules) you gain 0.10 Fortify Shout. Edit: Talos will no longer deny blessings for joining the legion as of 1.8

Zenithar: Fortify Barter +5, +3 each of at or more than: 100 weapons made, improved, 100 armor made, improved, 100 potions mixed. (total +20)

Nocturnal: Fortify Sneak +10, +3 each of at or more than: 100 backstabs, 100 locks picked, 100 sneak attacks, 250 items stolen, 200 pockets picked. (total +25). Exempt from the above Divines requirements; you may lie, cheat, steal, and murder all you want. Nocturnal doesn't care