A 57: Also from my lists of stuff... [spoiler]
Sneak AttackPHB
Rogue 1, 3, 5, 7.../20
DMG
Arcane Trickster: 2, 4, 6, 8, 10/10 (full caster advancement)
Assassin: 1, 3, 5, 7, 9/10 (Death Attack at level 1, gain minor arcane casting)
Blackguard: 4, 7, 10/10 (gain divine casting at level 1, full BAB)
Psionic
Pionic Rogue: 1, 4, 7, 10, 13, 16, 19/20
http://www.wizards.com/default.asp?x=dnd/psm/20040723bBook of Exalted Deeds
Slayer of Domiel: 1, 3, 5, 7, 9/10 (Death Touch at level 1, gain divine casting at level 1)
Sacred Strike, feat, against evil creatures roll d8 for damage instead of d6
Book of Vile Darkness
Cancer Mage: 1, 5, 9/10
Disciple of Baalzebub: 2, 5, 8/10
Complete Warrior (all full BAB)
Dark Hunter: 3/5 (Death Attack at level 5)
Darkwood Stalker: 3, 6, 9/10 (Death Attack at level 10)
Invisible Blade: 1, 3, 5/5 ("dagger" only, faint as free action 1/round)
Justiciar: 1, 4, 7, 10/10 (nonlethal strike)
Ronin: 1, 4, 7, 10/10
Complete Divine
Black Flame Zealot: 3, 6, 9/10 (Death Attack at 1, advances divine half)
Temple Raider of Olidammara: 2, 5, 8/10 (gain divine spells at level 1)
Complete Arcane
Complete Adventurer
Ninja: 1, 3, 5, 7.../20 (Sudden Strike)
Spellthief: 1, 5, 9, 13, 17/20 (gains arcane casting at level 4)
Daggerspell Mage: 3, 6, 9/10 (advances arcane 9/10)
Daggerspell Shaper: 3, 6, 9/10 (advances divine 9/10)
Dread Pirate (dishonourable): 3, 7/10 (full BAB)
Ghost-Faced Killer: 2, 5, 8/10 (Sudden Strike, full BAB)
Nightsong Enforcer: 1, 4, 7, 10/10 (full BAB)
Nightsong Infiltrator: 4, 8/10 (Teamwork Sneak Attack)
Shadowbane Inquisitor: 4, 7, 10/10 (full BAB)
Shadowbane Stalker: 3, 6, 9/10 (advances divine 8/10)
Shadowmind: 2, 5, 8/10 (advances manifesting class 7/10)
Spymaster: 3, 6/7
Streetfighter: 3/5
Complete Psionic
Lurk: 2, 7, 12, 17/20 (psionic sneak attack, only functions while psionically focused)
Ebon Saint: 3/5 (sneak attack or psionic sneak attack)
Complete Mage
Unseen Seer 1, 4, 7, 10/10, ecl 6 (either sneak attack, sudden strike, or skirmish; full arcane advancement)
Complete Scoundrel
Avenging Executioner: 1, 3, 5/5 (sudden strike, gain abilities to make opponent flatfooted)
Cloaked Dancer: 2, 4/5 (suprise strike, 3/5 arcane advancement)
Mountebank 2, 5, 8/10, ecl 7, Complete Scoundrel
Psibond 3, 6, 9/10, ecl 8, Complete Scoundrel
Master of Masks 1, 4, 7, 10/10, ecl 6, only while wearing the Assassin Mask
spellwarp sniper 2, 4/5, ecl 8, (sudden raystrike, see text)
Complete Champion
Mythic Examplar (Dardallion): 3, 5, 7, 9/10 (early entry ecl 5, advances casting 4/10)
Deities and Demigods
Justiciar of Taiia: 1, 4, 7, 10/10, ecl 6 (gain minor divine spellcasting at level 1)
Draconomicon
Dragonstalker: 2, 4, 6, 8, 10/10 (gains 2d6 sneak attack each time, only effective against dragons, full BAB)
Dragon Magic:
Hand of the Winged Masters: 2, 5, 8/10, ecl ?? (sneak attack or sudden strike or skirmish)
Dragon Descendant 3 (subtle ancestor), ecl 8: gain 2d6, see text (also stacks for certain monk abilities)
Fiendish Codex II - Tyrants of the Nine Hells:
Hellbreaker 3, 6, 9/10 (can also steal spell-like or supernatural abilities)
Cityscape
Ebonmar Infiltrator: 2, 5, 8/10, ecl 7 (gain minor Int based arcane casting)
Dungeonscape
Frostburn
Heroes of Battle
Dread Commando: 1, 3, 5/5 (Sudden Strike, full BAB)
Libris Mortis
Lords of Madness
Magic of Incarnum
Umbral Disciple: 2, 5, 8/10
Miniatures Handbook
Skullclan Hunter: 3, 6, 9/10 (can "sneak attack" undead at level 2, read "Divine Strike" wording carefully, not actually sneak attack... I think)
Tactical Soldier: read "Flanker" ability
Planar Handbook
Fatemaker: 3, 6, 9/10 (gains minor Cha based arcane casting)
Races of Destiny
Chameleon: see text
Menacing Brute: 3/5 (full BAB)
Scar Enforcer: 3,6,9/10 (advance half caster)
Races of the Dragon
Dragon Devotee 2, 4/5, ecl 7, (either sneak attack, sudden strike, or skirmish; advances sorcerer casting 2/5)
Races of Stone
Blade Bravo: 4, 8/10 (melee only, full BAB)
Stonedeath Assassin: 2, 4/5 (Stonedeath Strike at level 5)
Races of the Wild
Whisperknife: 2, 5, 8/10 (full BAB)
Sandstorm
Scorpion Heritor: 2, 4, 6, 8, 10/10
race: Marrulurk, small Monstrous Humanoid, 3 HD, +1 LA (ECL 4), 2d6 sneak attack
Stormwrack
Scarlet Corsair 2, 6, 10/10 (full BAB, faint as free action once per 2d4 or 1d4 rounds)
Tome of Battle:
Assassin's Stance, Shadow Hand Stance - gain 2d6 sneak attack
Tome of Magic:
Andromalius vestige - see text
Malphas vestige - see text (sudden strike)
Shadowblade 2, 4, 6, 8, 10/10 (sudden strike, at level 3 gain ability to deny opponent their dex bonus)
Expedition to Castle Ravenloft
Rogue 3: "Penetrating Strike" - exchange trapsense for the ability to do half you sneak attack damage against undead
Eberron Campaign Setting
Eberron: Five Nations
Dark Lantern: 2, 4, 6, 8, 10/10
Magic of Eberron
Vigilant Sentinal of Aerenal: 2, 4/5
Eberron: Secrets of Xen'drik
Scorpion Wraith: 1, 3, 5/5 (sudden strike, full BAB)
Eberron: Secrets of Sarlona
Fist of Dal Quor: 1, 3, 5/5 (sudden strike, also gain stunning attacks)
Eberron: Faiths of Eberron
Thief of Life: 2, 6, 10/10
Forgotten Realms Campaign Setting (3.0)
The Divine Seeker: 2, 4/5
Guild Thief: 1, 3, 5/5
FR: Champions of Ruin
Justice of Weald and Woe: 3, 7/10 (death attack at level 10, gain minor diving casting)
Night Mask Deathbringer: 4, 8/10
Shade Hunter: 4, 8/10 (gain minor arcane casting)
FR: Unapproachable East
Thayan Slaver: 4, 7, 10/10
FR: Lords of Darkness
Darkmask: 3/5
FR: Lost Empires of Faerun
Cultists of the Shattered Peak: 2, 4/5 (Death Attack at level 5, gain minor arcane casting)
Magelord: 1, 5, 9/10 (full arcane advancement)
FR: Races of Faerun
Warsling Sniper: 1, 3, 5/6, ecl 6, warsling only
FR: Player's Guide to Faerun
Shadow Thief of Amn: 1, 3, 5/5
Zhentarim Spy: 2, 4/5
FR: Serpent Kingdoms
Fang of Sseth: 1, 4, 7, 10/10
FR: Shining South
Crinti Shadow Marauder: 2, 4/5 (Sudden Strike, gains a "Shadow Pounce" at level 5)
FR: Silver Marches
Orc Scout: 3/5
Peerless Archer: 1, 4, 7, 10/10 (ranged only)
FR: Underdark
Imaskari Vengeance Taker: 3, 5, 7, 9/10 (half arcane advancement)
FR: Drow of the Underdark
Dread Fang of Lloth: 1, 3, 5, 7, 9/10 (sudden strike, full BAB)
Eye of Lloth: 2, 5, 8/10 (half caster)[/spoiler]