I like Preditors & Editors
because it is a great resource about publishing and writing. Look at the categories -- it has everything from Agents & Attorneys to Workshops. It's a great way to find out the inside scoop on the publishing industry. I hadn't visited the site in awhile, but when I stopped by recently it had a plea for visitors to contribute to the Preditors & Editors legal defense fund. Apparently, P & E is being sued by some people who don't like all the information that is divulged at the site, and they're asking for donations to help them mount a defense in court. It's a good cause, and I hope people help them out.
In the meantime, if you just want to research a magazine, an agent, a publisher, or anything else related to publishing, P & E is the site for you.