Here's an interesting Warlock DPS calcluator. It only does level 70 spells though, which is a bummer for those of us taking it slowly!

Ybrith, of Rajaxx (Eu), has put together a lovely piece of theorycrafting apparatus. This warlock DPS calculator takes your stats and talent information, the length of the fights you're interested in, and a few strategy parameters, and comes up with your DPS over the length of the fight, as well as how fast you would be losing life. It seems to be geared towards the end-game, as it's based on level 70 spells and also not suited for calculating things like mana efficiency, which is important in leveling.