I need help finding an agent for publishing my second novel - how do I find a legitimate agent?

[Laura]

Okay, so a few things.
I have already published a book, so I'm aware of the publication process and I'm aware you don't NEED an agent to publish a book. I also know that it will be difficult to find a willing author in this economy.
Please, unless you actually KNOW don't answer this. I know that I could easily type "agents" into an internet search box and find a slew of them, but I'm more concerned with knowing sources to find LEGITIMATE agents - not just any type.