When you're running an event, sometimes you want to help lots of people create accounts on Wikimedia sites. To prevent spamming/vandalism, ordinarily there's a cap on the number of accounts that can be created from one IP address in a single day. But there's a way to ask for a temporary removal of that restriction. The Foundation's Maggie Dennis has written a quick HOWTO:
http://meta.wikimedia.org/wiki/How_to_request_lift_of_an_IP_cap
and so please feel free to link to it in your outreach HOWTOs, event planning checklists, and so on. Thanks, Maggie!