I've been to three conferences, and all were worth the time and money. The first one I went to was the Southern California Writer's Conference, which was good but made me feel like I was suffocating. (Could have been because it was my first one.) After that, I joined SCBWI (society of children's book writers and illustrators) and then went to their L.A. conference--twice (even though I moved across the country and it cost a whole lot more). I have met new best friends, got inspired, found my literary agent (although I didn't actually MEET her at the conference--just thought she was good), and got immersed.
One other thing you can do is join an organization, such as the SCBWI. There are lots of them out there--I know there's one for Romance writers, and there's got to be some for Sci-Fi fantasy.
What do you write?
If you write kid-oriented stuff, check out www.scbwi.org