I took a quiz on the Dungeons and Dragons website. It's supposed to be used to determine what alignment is suggested for your character, but I believe it could be used to determine your own alignment.

Here it is.

I, as I expected, received Lawful Good.

A lawful good character acts as a good person is expected or required to act. She combines a commitment to oppose evil with the discipline to fight relentlessly. She tells the truth, keeps her word, helps those in need, and speaks out against injustice. A lawful good character hates to see the guilty go unpunished. Lawful good is the best alignment you can be because it combines honor and compassion.

--excerpted from the Player’s Handbook, Chapter 6