Mathowie has turned MetaFilter signups back on, for a $5 one-time fee. Totally worth it. I hope the MeFi stats get updated, or Matt announces how many new signups there were today. I’m user #17646.
Update 11-19: Matt got enough signups to pay for a full year of webhosting! My calculations show roughly 1200 new users in the last 24 hours, although there are certainly people who bailed between signup and donate in that count.