Since ability focus varies by pact (and, in the case of Star Pact warlocks, even within pacts), warlocks will be referred to as Cha-focused or Con-focused. An additional score may be given for Hexhammers (constitution based melee warlocks).
Player's Handbook Edit
Dragonborn: Their stat bonuses make them decent choices for Cha-based warlocks; additionally, their benefits from Con (higher healing surge values and damage from breath weapon) synergize well with a Con-based warlock. A minor action area of effect racial power isn't bad, though your move and minor actions are often already spoken for as a warlock (maintaining concealment and spreading your curse, respectively). 3/5, 4/5 for Hexhammers.
Dwarf: Their Constitution bonus is good for Con-focused warlocks, and their second wind as a minor action is good for anyone. Their lower mobility may be a problem as a striker. Access to pact hammers and dwarven weapon training makes them execellent hexhammers, though. 3/5, 5/5 for Hexhammers.
Eladrin: They only have a bonus to a secondary stat, though their teleportation ability will be appreciated (particularly by feytouched warlock). 2/5.
Elf: Stat bonuses are unhelpful. The high mobility and racial power are all that keep this from being a 1. 2/5.
Half-Elf: With Constitution and Charisma bonuses, this is the only race good at pulling off being both Con- and Cha-focused, either as a starpact warlock or any warlock that eyes powers from pacts outside his own. Dilettante may not be useful, as there are few at wills outside your class based on Constitution or Charisma- look to paladin and the upcoming bard for Charisma powers. Constitution based Half-Elves may be out of luck and may need to look for intelligence-based powers instead. 5/5 for Con/Cha warlocks, 4/5 if you're not splitting your focus.
Halfling: Excellent Cha-focused warlocks, with racial abilities that assist mobility and avoiding being hit. 4/5.
Human: They can use their stat bonus to be good at either type of focus, and are the only warlocks that get an at-will from outside their pact. An extra feat and skill are never a bad thing, either. 4/5.
Tiefling: Their stat bonuses make them perfect for any Cha-based pact. Being able to pick up a bonus to hit with fire powers (which don't come up much for Cha pacts) and fear powers (which do) is good, too. 5/5.
Monster Manual Edit
Bugbear: Stat bonuses and oversized weapons are unhelpful. 1/5.
Doppleganger: Like tieflings, are good Cha-focused warlocks. They won't be as strong in combat, but their out of combat abilities are certainly something to consider. 4/5; 5/5 if your campaign is roleplay heavy so you can take advantage of shapeshifting often.
Githyanki: Ability score bonuses are perfect for Con-focused warlocks; the bonus to Initiative and flying power (for you or a party member) are nice too. 5/5.
Githzerai: No useful ability bonus, though the racial abilities are nice. 2/5.
Gnome: Perfect ability bonuses for Cha-based warlocks, plus reactive stealth and fade away are excellent abilities. The racial stealth bonus is nice, too. 5/5
Goblin: Decent Cha-based warlocks; their racial ability in particular is nice for getting away from melee types. 4/5.
Hobgoblin: Like half-elves, they can focus in either Con, Cha, or both. The immediate saving throw isn't bad, either. 4/5.
Kobold: Good Con-based warlocks; shifty is nice for getting away from melee, though it means not cursing anyone in a round you use it. 4/5.
Orc: A Con bonus and racial abilities focused towards melee make these decent hexhammers. 3/5, or 4/5 for hexhammer.
Shadar-kai: Similar to the eladrin, just shadow/dark flavored instead of fey flavored. 2/5.
Longtooth shifter: No useful ability bonuses and racial abilities that only trigger when you're bloodied aren't great. 1/5.
Razorclaw shifter: See longtooth shifter. 1/5.
Manual of the Planes Edit
Bladeling: The only good thing is their racial power; dragonborn are better if that attracts you. 1/5.
Forgotten Realms Player's Guide Edit
Drow: Ability bonus make this a good Cha-based warlock and either racial ability can be used for free combat advantage. Cloud of darkness can also be used to get out of a sticky situation by blinding surrounding enemies. 4/5.
Genasi: The Int bonus is nice, as are some of the possible racial abilities, but generally not worth it. 2/5.
Dragon Magazine (Issue #) Edit
Gnoll: Good for Con-based warlocks; good mobility, but the racial powers likely won't come into play unless you're a hexhammer. 3/5, 4/5 hexhammer.
Minotaur (#369): A good Con-based warlock; a better hexhammer, expecially if using the original oversized weapon version. 3/5, 4/5 hexhammer.
Warforged (#364): Good for Con-based warlocks. Hexhammers can use a two handed hammer and an embedded rod; others can hold two rods and embed two more for lots of properties. 5/5, hexhammer 5/5.