I used to use
active guestbook - it worked pretty well. I like guestbooks. Gives people a chance to come in and say hello quickly and easily, and they can give you feedback too. If your forum wasn't active enough to keep the guestbook is definately the way to go.
I eventually coded my own though so I could have messages instantly posted but retain URLs for approvals. I kept getting these ****ing german spammers all the time, it really pissed me off because there'd be these friendly high schoolers with geocities pages and then suddenly some idiot posting in non-english about a .de viagra site. i'm still mad just thinking about it.