Incidentally, I found the Comprehensive Guide to Turning
, but it's not very good.
The suggestion Vaz made in that GiantITP thread doesn't work, as an undead cannot Alter Self into a Dusk Giant (which is a Giant, not an Undead). Polymorph would allow you to turn into a Dusk Giant, but it's very sketchy in a lot of ways and wouldn't be able to get up to turning a Winterwight anyway.
The important things to boost for turning and rebuking are times/day (mostly for divine feats) and effective rebuking level (to control bigger stuff). Boosts to the turning check and turning damage are largely irrelevant, and effective turning level's only relevant if you can perform a Greater Turning (and even then, not as much as rebuking level).
What I know of to boost them is the following:
Extra Turning (+4 to all turning and rebuking attempts/day; if you have multiple pools it's +4 to each; stacks with itself)
Improved Turning (+1 turning/rebuking level)
Amulet of Undead Turning (3.0
DMG, 11k): +4 turning level. Was converted into the Phylactery of Undead Turning for 3.5.
Ephod of Authority (MIC, 800gp): +1 turning level. Specifically doesn't work on rebuking.
Flametouched Iron holy symbol (Eberron Campaign Setting, 750gp): +1 turning level. Unlikely to work on rebuking, since the material's good-aligned, and unlikely to be exported from Eberron since it's an Eberron material.
Icon of Ravenloft (Expedition to Castle Ravenloft, 18k): +4 turning level when used as a holy symbol (unlikely to work on rebuking, since it's a [good] item and only mentions turning).
Lyre of the Restful Soul (LM, 3k): when played (DC 15 Perform(string)), undead within 60ft get -4 penalty to turn resistance for 1 minute. Can reduce turn resistance below 0, but not below 1 effective HD.
Moonfriend (Expedition to Castle Ravenloft, 9k): +3 turning level. Specifically doesn't work on rebuking.
Nightstick (LM, 7.5k): +4 turn/rebuke attempts/day. Has text about "anyone who possesses the rod" which causes endless debates.
Phylactery of Undead Turning (DMG, 11k): +4 turning level (unlikely to work on rebuking, since it's a [good] item and only mentions turning).
Prefect's Vestments (Expedition to Castle Ravenloft, 6k): +1 turn attempt per day (unlikely to work on rebuking, since it's a [good] item and only mentions turning).
Reliquary Holy Symbol (MIC, 1k): +1 turn/rebuke attempt/day for each of three prereqs you meet (5 ranks Know(religion), any divine feat, Improved Turning). Throat slot. Specific to a deity.
Rod of Authority (3.0
DotF, 20,576 gp): +4 turning/rebuking level, cast Command 3/day at CL 9 (not Command Undead).
Rod of Defiance (LM, 13k): +2 heavy mace. Undead within 30 ft of wielder "are treated as if they had -4 turn resistance"; how this is interpreted* determines whether it's brokenly good or merely good.
Rod of the Dead (FR: Underdark, 75k): +4 rebuking level for wielder, Animate Dead by touching a corpse (20 HD/day limit).
Sacred (BoED, +2): Armor/shield enchantment that gives +2 to turning/rebuking level. Not stated whether sacred armour + sacred shield stack. Specific to a deity.
Scepter of the Netherworld (MIC, 9k): +3 turning/rebuking level for wielder.
Sword of Crypts (3.0
A&EG, 42,315 gp): +2 holy longsword that gives +1 turn attempt/day to any cleric and +2 turning damage for clerics of Heironeous (unlikely to work on rebuking, since it's a [good] item and only mentions turning).
Sword of the Glorious Pearl (Stormwrack, 75,335 gp): +3 aquatic holy pearlsteel bastard sword that grants Extra Turning if you can turn undead (unlikely to work on rebuking, since it's a [good] item and only mentions turning). If the pricetag didn't dissuade you, there's also a whole prestige class that will come after you if you have one of these and are not an aventi.
*The two main interpretations I can see are a) that it reduces turn resistance by 4 (with the added question of whether this can go below 0), or b) that it sets
turn resistance to -4 regardless of its previous value. The latter reading lets you enslave CR-appropriate liches and vampires.
Further note: it's vaguely dubious whether a lot of the level-boosters stack, since most of them use the text "X levels higher than it actually is". Sacred should definitely stack with other boosters, and Scepter of the Netherworld should with its MIC wording.