I'm pretty sure I used
Japan Guide to find my language exchange friend. Unless you're speaking with a very advanced learner, you're likely to be exposed to unnatural or even incorrect Japanese, so you're much better off practising with a native. You also have the added advantage of all their cultural insight, and you can get some help with your speaking through Skype as well.
I had my first voice chat yesterday with my friend who I've been e-mailing for about a year, and it went really well. It's the first time I've ever spoken Japanese with someone, but I managed to get through 3hours of it somehow. I kept putting it off, but it turned out to be really fun, I learnt a few things, and have a lot more confidence in my speaking. I definitely recommend throwing yourself into that situation as soon as you can: you won't regret it