How to encourage faculty involvement as judges in a local research exposé? Our university has a an annual event showcasing graduate student research projects and has a competition for best presentation.  However, faculty involvement (as judges for the event) was very sparse and we had a difficult time getting enough faculty to volunteer as judges.  I know that faculty time is very precious and this event did demand a lot of time and provided little incentive other than free food.  How else can I encourage more faculty involvement in this event?
We have the same kind of event, and we get reasonable faculty involvement. A few things that help:


Faculty are likely to show up and get involved if their students participate. Make sure students of many different faculty participate and remind the professors of this fact.
Remind, remind, remind. Send regular (but not daily) reminders to the faculty. Keep the emails short, and let them know what's expected of them - show up at this place, at this time, and encourage students. 
Get different people involved in different aspects: some might review the presentations, some might help with pre-screening, and so on. The more people are involved, the more they feel part-ownership, and the more likely they are to participate in other ways.
Do this regularly. It's often hard to do this the first time, but once it's a regular occurrence, people get used to the rhythm of it and how it fits into the calendar.