One of the (several) problems of the Warlock is that it just doesn't have enough Invocations, and while Eldritch Glaive and Hindering Blast represent a little love... that's about all they got from splatbooks.

These are NOT designed to 'fix the class'. That would require a re-write of the class itself, not merely adding options to the class. Indeed, one of the fundamental problems with Warlocks is that they only have 12 invocations. Indeed, by including these invocations into your campaign, your warlocks may feel it to be a nerf, because now they have a large number of choices... but a small number of invocations they can actually take.

Here's some additional invocations that I've created that might help out Warlocks:

LEAST

Eldritch Blade
Eldritch Shape invocation

You create a blade of coherent eldritch energy, which can be used as a weapon. The actual shape of the weapon can be any one-handed weapon, or even appear to be electrical charge flowing around the hand in question, however the shape does not, in the least, affect the mechanical properties.

Unlike most Invocations, this invocation only needs a Swift action to activate. The Eldritch Blade may be used as a melee touch attack which is considered to be armed, and deals Eldritch Blast damage. Attacking with the Eldritch Blade is considered to be an attack action.

The Eldritch Blade is considered to be a weapon, however it is immune to Disarm and Sundering, since it is not corporeal in any way.

If the Warlock wishes to maintain the Eldritch Blade, he may do so at the cost of a swift action each round.

The Warlock may not use Eldritch Blast for anything other than this invocation while it is being used or maintained.

If you wish to create two eldritch blades, you may do so, however each one deals half damage, round down.

Eldritch Knowledge

Allows the Warlock to use Identify as a SLA. Also grants a +2 Enhancement bonus to all Knowledge skill checks.

Eldritch Frivolity

Allows the Warlock to use Mage Hand, Open/Close, and Prestidigitation. The Warlock must choose which of these effects when he uses it.

LESSER

Exhausting Blast
Eldritch Essence

Fort save or be Exhausted

Eldritch Ball
Eldritch Shape

Shapes the eldritch force into a 10' radius circular spread. Ref/half

Eldritch Line
Eldritch Shape

Shapes the eldritch blast into a Line 30' long. Ref/half. If the Warlock is capable of applying multiple Eldritch Shapes to a single eldritch blast, combining this with Eldritch Spear will create a Line out to 120'.

GREATER

Infernal Skin

This functions as a self-only version of Stoneskin.

Anchoring Blast
Eldritch Essence

The target is also prevented from extradimentional travel, as per Dimension Lock, for one round.

Venomous Blast
Eldritch Essence

Fort save or 2 Con damage

Eldritch Sphere
Eldritch Shape

The Warlock summons a sphere of energy around him. Anyone attacking him with a melee attack, attempting to grapple, or otherwise attempting to enter the square he occupies, takes his Eldritch Blast damage, plus any Eldritch Essence he used on it. This sphere lasts one round.

Eldritch Wall
Eldritch Shape

The warlock summons a wall of energy 5' thick and 20'/lvl long. Anyone who enters the wall takes Eldritch Blast damage, plus any eldritch essence used. This wall lasts one round.

Paralytic Blast
Eldritch Essence

Will save or be Paralyzed for one round.

Forceful Blast
Eldritch Essence

Eldritch Blast becomes a Force effect.

DARK

Eldritch Eyes

Self only True Seeing. 24 hr duration

Mindless Mind

Self only Mind Blank. 24 hr duration

Dispel Barrier

The first dispelling or disjoining effect which targets invocations that you have used on yourself automatically fails. It does not protect your gear or any spells present upon you from sources other than your invocations, nor does it protect any effects caused by your invocations which are not targeting yourself.