Whether conducting a project kickoff, a seminar, or a training session, it's always fun to start with an ice breaker. It doesn't have to be anything fancy. I've seen ice breakers that were nothing more than a funny video, but served to loosen things up (nowadays that's pretty easy with YouTube, such as this one we posted on PMThink).
I've also seen ice breakers that served to get people moving around and networking, such as having each person use pictures (and no words) on a piece of folded flip chart paper to describe themselves, and then having people pair off for a minute at a time and interpret each other's pictures.
If you're looking for ideas, here's a nice list to help get you started. I think my favorite link is the last one.