I've been using Blog Explosion recently:
It certainly drives traffic to your site, but I have to say I'm sceptical about the **quality** of that traffic (no offence if that's what brought you here)
I'm philosophical about this for a couple of reasons:
1) I don't write this blog especially for an audience - I write it primarily for myself. I HOPE other people like it, but that's not why I do it.
2) I have found some really interesting blogs whilst surfing for credits (and a lot of other ones too...)
It's bloody addictive too.