I know you know, but it never hurts to remind people about the importance of proofreading everything connected to your event. Even (or especially) any giveaways, like t-shirts or coffee mugs or pens with your organization's name on it. Unless you don't mind being embarrassed the way Eugenio Velez of the San Francisco (or is that San Francicso?) Giants was recently. Ouch.
Thanks to Miriyah for the pointer!