Love 'em or not, they are a fact of life for most writers. Especially if you desire publishing with a major house such as Tor or Berkley. So, it's your job to learn all you can about agents and how they work. You have to learn what they require for submissions, what they represent and what they can do for you to improve your publication chances.
But where do you start?
Agent Query offers the largest, most current searchable database of literary agents on the web—a treasure trove of reputable, established literary agents seeking writers just like you. And it's free (not because there's a catch, but simply because not enough things in this world are free).
Miss Snark This "secret" agent blog isn't active but the archives are stuffed full of great info. I suggest you go all the way back to the beginning and start reading there. If you look hard enough...you'll find where I won "Best Use of a Blog Joke" in one of her writing challenges. And while you're there, clink on some of the other agent links and check them out too.
One of my favorite agent blogs is that of agent Janet Reid. Even if you write things she doesn't represent, you should read this blog for all the great info. It's on my list of daily reads. She has a nice list of agent links too.
Twitter is also another place to find agents. I "follow" quite a few there and it's interesting to see a more informal side of them. Twitter is also a great place for writing tips, quotes and articles.
And while you are learning about agents, here's a great place to learn about query letters.