I'm thinking of adding a forum to an established blog site.

What is the best forum script to use which will integrate well with wordpress? I don't make users register to post a comment, so I don't have to worry about existing members.

I have checked out bbpress which is from the same creators as wordpress, but integration looks like a mess.

Any other suggestions? Please don't suggest vBulletin, I know it's a good forum but I don't want to pay for a script considering the forum is not the main part of the site, I just want to get a bit of a discussion happening.