Best tools for keeping the task of moderation manageable...

I'm building a social network, and I'm wondering how best to minimize the amount of effort I need to put into moderation, while keeping the site from being taken over by trolls and spammers. I'm looking at "troll", "ignore user", and Mollom. I'd love to hear what combinations have proven successful, and any other techniques you'd recommend. I'm planning to start with an invitation-only beta, where people pass invitations on to their friends, and hopefully that will lead to a good core group of legitimate users.

Thanks for any insight,

Ln