PANTS

Best overall: Earthgiving Legguards, a Leatherworking BoE.

Best drop: Skirt of the Old Kingdom or Kilt of the Forgotten One, both (weirdly enough) from Herald Volazj in heroic Old Kingdom.

Best quest piece: Leggings of Heightened Renewal from the quest The Iron Colossus in Storm Peaks.

Best faction piece: Giant-Friend Kilt, available at revered with the Sons of Hodir. These are really oriented more toward Balance, but surprisingly they're the only caster legs available with Wrath factions.

Runner-up: Cyanigosa's Leggings from Cyanigosa in heroic Violet Hold, Opposed Stasis Leggings off Commander Stoutbeard/Commander Kolurg in heroic Nexus, or Breeches of the Caller from Ingvar the Plunderer in heroic Utgarde Keep.

Enchant: Sapphire Spellthread or Brilliant Spellthread, depending on how optimistic you are concerning your health versus mana regen. Have fun farming those eternals!
FEET

Best overall: Arcanic Tramplers, a BoE from Malygos-25. If you are very, very lucky, these will start showing up in /trade or the AH as raids gear up and guilds start selling BoE pieces, but they won't come cheap.

Best drop: Cleric's Linen Shoes from Commander Stoutbear/Commander Kolrug in heroic Nexus, Boots of Transformation from Gal'darah in heroic Gun'drak, or Footwraps of Teleportation from Xevozz in heroic Violet Hold.

Best quest piece: Fur-Lined Moccasins from the quest One of A Kind in Zul'drak/Gun'drak, or The Darkspeaker's Footpads from the quest Mind Tricks in Icecrown.

Best faction piece: Sandals of Crimson Fury, available at exalted with the Wyrmrest Accord.

Runner-up: Earthgiving Boots, a Leatherworking BoE.

Enchant: Either Enchant Boots -- Greater Spirit or Enchant Boots -- Tuskarr's Vitality depending on your gear set and playstyle. You can also slap Enchant Boots -- Greater Vitality on, and that's fine too, but assuming you have the Spirit-related talents in the Restoration tree, Greater Spirit will do more for you (and scale better) than 6 mp5.


RINGS

Best drop: Spectral Seal of the Prophet, from the Prophet Tharon'ja in heroic Drak'tharon, or Band of Guile from the Dark Runed Chest in heroic Culling of Stratholme

Best quest piece: Lion's Head Ring, from the quest For Posterity in Zul'drak/Gun'drak, or Flourishing Band, from the quest The Struggle Persists in the Oculus.

Best faction piece: Signet of Hopeful Light, available at exalted with the Argent Crusade.

Runner-up: Titanium Spellshock Ring, a BoE from Jewelcrafting.

Enchant (if applicable): Enchant Ring -- Greater Spellpower.
TRINKETS

Best overall: Darkmoon Card: Greatness. Yes, the intellect version is actually better than the spirit version, consequence of how our mana regeneration from spirit scales with intellect. Unfortunately, you're going to be scrambling for Nobles cards alongside every other poor bastard on your server, so don't count on being able to get this quickly unless you're willing to burn through upwards of 20,000 gold.

Runner-up, courtesy of the fact that only horse thieves and murderers will have Nobles Decks: The Egg of Mortal Essence, available for 40 Emblems of Heroism.

Best drop: Soul Preserver from the Dark Runed Chest in normal Culling of Stratholme, Talisman of Troll Divinity from the Prophet Tharon'ja in heroic Drak'tharon, Spark of Life from Sjonnir in heroic Halls of Stone (ugh, +haste, ugh), or Tome of Arcane Phenomena from the Cache of Eregos in heroic Oculus.

Best quest piece: Cannoneer's Morale, from the quest The Last Line of Defense in Icecrown. You can also use any of the usual green +spellpower trinkets granted by quests while leveling. I confess to being rather interested by the Futuresight Rune, a reward from Mystery of the Infinite, Redux in Dragonblight.

Best faction piece: There's nothing truly relevant in this slot, although you can use the Frenzyheart Insignia of Fury or Oracle Talisman of Ablution if you're really desperate.

Additional runners-up: Figurine -- Sapphire Owl for Jewelcrafters or Mercurial Alchemist Stone for Alchemists.

Important note: Aertimus at Hotstree makes the point that one of the best trinkets (if not the best) for Restoration druids remains Darkmoon Card -- Blue Dragon. I don't yet have this and haven't been able to test the proc rate at 80, but if Blizzard hasn't nerfed it (and according to Wowhead commenters, they haven't), then Aertimus is 100% accurate. Keep an eye out for Beasts cards.
WEAPON

Best overall: Staff of Draconic Combat, from the Cache of Eregos in heroic Oculus.

Best drop: War Mace of Unrequited Love from Keristrasza in heroic Nexus, or Netherbreath Spellblade/Staff of Wayward Principles from Skadi the Ruthless in heroic Utgarde Pinnacle. Bonus: the Spellblade's graphic is very sword-like, which is kind of a novelty for Druids.

Best quest piece: Screw-Sprung Fixer-Upper, from the quest The Champion of Anguish in Zul'drak.

Best faction piece: Gavel of the Brewing Storm, available at revered with the Wyrmrest Accord.

Runner-up: Titansteel Guardian, a Blacksmithing BoE.

Enchant: Hands-down it's Mighty Spellpower, but this is hellishly expensive in the early days of an expansion with very few people willing to disenchant epics. You can use Enchant Weapon -- Exceptional Spellpower in its place, or try Enchant Weapon -- Exceptional Spirit.


OFF-HAND

Best overall: Handbook of Obscure Remedies, available for 40 Emblems of Heroism.

Best drop: Temple Crystal Fragment, from Novos the Summoner in heroic Drak'tharon Keep.

Best quest piece: The Witching Grimoire, from the quest Banshee's Revenge in Icecrown.

Best faction piece: The only item in this slot from faction vendors is going to be the Darkspear Orb for Horde/Orb of the Eastern Kingdoms for Alliance, available at revered with your respective faction in Northrend (Horde Expedition/Alliance Vanguard). Not that great either way.

Runner-up: Frostbridge Orb, a BoE off heroic Oculus trash.