[3.5] Increasing Warlock Versatility

[Extra Anchovies]

What ways are there for a Warlock to broaden his area of expertise while still focusing mostly on Invocations? The two most obvious ones are Eldritch Disciple and Eldritch Theurge (using early-entry tricks for both), with a prepared caster on the non-warlock half. There's also Chameleon; a two-level dip means two lost caster levels, but that extra bonus feat could be used for item creation feats or for Extra Invocation [whatever seems useful that day]. Any others that you know of?

[Troacctid]

Skill points? Urban Savant is a great prestige class for Warlocks--easy to qualify for and offers 10/10 casting progression with 6 + Int skill points per level, plus a side order of metagame knowledge.

Edit: Unseen Seer and Prestige Bard do something similar, although they cost you caster levels.

[Rebel7284]

A binder dip has many uses.

[aleucard]

A cleric dip would probably add as much here as it would anywhere else. Monk on a Clawlock would be interesting, though something to at least emulate Pounce would be especially useful; I've personally used a Swordsage dip for similar purpose, and that went fairly well while the game lasted. Chameleon 2 is a painfully obvious option for if you want 24-hour access to any feat (read: any Invocation 1 level lower than your max, plus all other sorts of madness). The utility of things like Wizard and Psion are going to be limited unless if you're going for something like a Theurge build, but they can have their uses. Nothing else really comes to mind, though.