Thanks to the miracle of cyberspace, we have access to agents and editors who openly share their business lives with the rest of us through their sites and blogs. There are a few that I've seen many writers link to on their blogrolls, and one such is Nathan Bransford. This guy has such good advice and a sense of humor, to boot. I check his blog daily and have made lots of good notes.
There are so many good agent blogs out there, but another that I frequent is LDS Publisher. She gives valuable advice specific to the LDS market, so if that's your goal, your time will be well spent at this blog.
One last blog with a wealth of info: BookEnds LLC. So, so much good stuff to be had there. BookEnds is a literary agency and I love the conversational, helpful and friendly tone of the posts. Makes you feel like you can get there from here.
Good luck, and might I suggest a massive Google hunt for agents/editors if you want to get an overall feel for who's out there and who might be representing the kind of books you write. If you're like me, the hunt is half the fun. I love doing industry research. If you're not like me, however, then just visit the links I've provided, for starters, and work from there. :-)